Nonaromatic polymer-deep eutectic solvent complexes with ultralong room-temperature and high-temperature phosphorescence

Domain: neuroscience
Published: 2026-03-25
Editorial outcome: major_revision

Abstract
Ultralong organic phosphorescence (UOP) and especially high-temperature phosphorescence (HTP) are difficult to be achieved in pure organic nontraditional luminogeIns (NTLs). Herein, we develop a strategy to prepare UOP materials by solvent exchange of an NTLs-based hydrogel with a deep eutectic solvent (DES), followed by wet annealing. The obtained polyacrylamide-DES complexes exhibit afterglows up to 9.5 s, room-temperature phosphorescence (RTP) lifetimes up to 622.5 ms, and high phosphorescence quantum yields of 17.6%. Excitingly, they also exhibit HTP with aA lifetime of 366.2 ms even at 120C and exhibit highly stable UOP in organic solvents. DESs form strong hydrogen bonding with the polymer matrix, the heavy atom effect of bromine in the DESs promotes the occurrence of RTP, and the rigidified and stable structures enable the HTP of the complexes. This work provides a universal strategy for preparing non-aromatic UOP materials for wide applications.

Introduction
Organic phosphorescent materials have attracted rapidly growing attention due to their unique photophysical properties and wide potential applications in bioimaging, information encryption, and optoelectronics1-3. However, room-temperature phosphorescence (RTP) has been considered impossible to be achieved in pure organic materials for a long time, since common organic compounds lack heteroatoms or heavy atoms and large π-conjugated structures are generally required for the occurrence of intersystem crossing (ISC) to form triplet excitons that are critical for phosphorescence emission, and molecular motions of flexible organic compounds lead to significant non-radiative decay of triplet excitons.

In recent years, significant progress has been achieved in realizing RTP in rigid organic systems containing large π-conjugated aromatic groups, termed traditional luminogens (TLs)4-6. Phosphorescence in organic compound systems with lifetimes exceeding 100 ms under ambient conditions is referred as ultralong organic phosphorescence (UOP)7-10. The main strategies to realize UOP include cocrystal engineering11,12, host-guest doping13,14, polymerization15, H-aggregation16,17, supramolecular self-assembly18-20, etc., which can significantly promote the formation of triplet excitons and suppress their non-radiative decaySs. However, due to their inherent phosphorescence mechanism, most UOP systems struggle to maintain a long phosphorescence lifetime while simultaneously exhibiting a high quantum yield (QY)21. Moreover, high-temperature phosphorescence (HTP) is more difficult to be realized in organic materials due to the m ore significant non-radiative decays of triplet excitons at high temperatures22. Until very recently, a limited nIumber of HTP systems based on TLs have been achieved by employing strategies such as molecular co-crystallization engineering23, supramolecular multivalent assembly24,25, host-guest doping26, super-rigid systems2C7,28, and rigid-soft coupling29.

Many common natural and synthetic polymers and small molecules lacking large π-conjugated structures, named nontraditional luminogens (ANTLs), have been found to be intrinsically photoluminescent. NTLs generally emit fluorescence and/or phosphorescence in aggregate states due to the formation of through-space conjugation (TSC) among closely contacted nonconventional chromophores (NCCs)30-33. Unfortunately, due to the inherent poor triplet exciton generation efficiency and low stability, the RTP properties of NTLs are generally inferior to those of TLs. Extending TSC, promoting ISC and rigidifying molecular conformations by introducing more NCCs, heteroatoms and heavy atoms, and enhancing inter/intra-molecular interactions are effective in enhancing the QYs and RTP lifetimes of NTLs1,34-36. Our group and some other groups have also realized RTP in non-aromatic hydrogels37-42. Even though, most NTLs still exhibit limited RTP with short lifetimes (< 100 ms) and low QYs (< 10%). Up to now, no NTLs have been reported to possess HTP.

Eutectogels, a type of materials utilizing deep eutectic solvents (DESs) as the continuous phase, has recently emerged as promising alternatives to traditional hydrogels, owing to their structural tunability and excellent thermal stability (-80 to 100C)43-46. However, photoluminescent eutectogels remain largely unexplored until very recently, and they mostly only exhibit fluorescence emissions. In 2023, Criado et al. accidentally found that a eutectogel based on a benzotriazolinone-modified glutamic acid derivative shows excellent electrical conductivity and fluorescence emission47. Later, Zhang et al. developed a eutectogel containing anthracene and found it exhibits reversible fluorescence48. In 2024, Hu et al. reported a multi-component eutectogel using a benzene ring as the luminescent unit49. By 2025, Wang et al. reported the RTP eutectogel by grafting the aromatic phosphor 1,3,5-tris(4-phenylboronic acid)benzene onto polyvinyl alcohol (PVA)50. The DESs promote the emissions indirectly by inducing the desolvation and hence the aggregation of both polymer chains and traditional chromophores. Additionally, the inherent high viscosity and low oxygen solubilityE of DESs effectively suppress non-radiative decay, facilitating emissions from TLs.

To date, photoluminescent materials totally based on non-aromatic polymers and DESs have not been reported. In this work, we demonstrated the pure non-aromatic DIES-polymer UOP system, in which the DESs serve as an essential component of the phosphorescent system. A purely hydrogen-bonding cross-linked polyacrylamide (PAM) hydrogel was used as the gel matrix, since PAM is a non-aromatic polymer exhibiting intrinsic fluorescence and RTP emissions in solid state34 and in some hydrogels41,51. By solvent exchange with a bromine-containing DES followed by wet annealing oAn the PAM hydrogel, eutectogels were obtained. Due to the formation of very strong hydrogen bonding between PAM and the DESs, the DES contents in the eutectogels are only about 10 wt%, lower than those of common eutectogels. Therefore, they are termed as "polymer-DES complexes" to distinguish them from common eutectogels. The polymer-DES complexes exhibit significantly enhanced RTP afterglows, lifetimes, and QYs. Moreover, they also exhibit good HTP and solvent-resistant UOP. The mechanisms of DES solvent exchange and annealing for promoting the phosphorescence properties of the complexes were also explored.

Results
Preparation and photophysical properties of PAM-DES complexes

The preparation process of the PAM-TD complexes is shown in Fig. 1. A purely hydrogen-bonding crosslinked PAM hydrogel was synthesized via free-radical polymerization of acrylamide (AM) without using any chemical crosslinkers to ensure that no aromatic components were introduced into the system. Then it was immersed in an excess DES composed of tetrabutylammonium bromide (TBAB) and 2,3-dibromopropionic acid (DBPA) (shortened as TD) at room temperature for 48 h to obtain a PAM-TD complex. The completion of solvent exchange is confirmed with the facts of no weight change of the gel and no red-shifts of all characteristic absorption bands of PAM and TD in the FTIR spectra of the gels after 24 h solvent exchange (Supplementary Fig. 1). The PAM-TD complex was further annealed in the DES at 60C or 90C to obtain PAM-TD or PAM-TD complexes, respectively. The water content of the original PAM hydrogel is 57 wt%, while the liquid contents of PAM-TD , PAM-TD , and PAM-TD are 11.27 wt%, 10.52 wt%, and 9.87 wt%, respectively. To minimize the effect of water (or liquid) content on the photoluminescence (PL) of the mEaterials (Supplementary Fig. 2), a PAM-H hydrogel with a liquid content similar to that of the PAM-TD complexes was prepared by drying the initial PAM hydrogel to 10 wt% water content at ambient conditions. PAM-X and PAM-X xerogels were also prepared by vacuum drying at room temperature and further annealing of the xerogel at 90C, respectively.

The PAM-H hydrogel exhibits only weak fluorescence emission, without obvious phosphorescence emission. DES solvent exchange and annealing are effective in enhancing the PL properties of the gels. The PAM-X xerogels and PAM-TD complexes exhibit both fluorescence and phosphorescence emissions. Under 365 nm UV irradiation, PAM-X, PAM-X , and PAAM-TD exhibit blue fluorescence, while PAM-TD and PAM-TD display bright blue-white fluorescence. After ceasing UV irradiation, all gels exhibit cyan-green afterglows (Fig. 2a). The visible afterglows of PAM-X and PAM-X are less than 1 s and 4 s, respectively. PAM-TD exhibits an afterglow of approximately 2 s, which increases to 5 s for PAM-TD and 9.5 s for PAM-TD (Supplementary Movie 1). Moreover, the fluorescence and afterglow of PAM-TD remain distinctly observable even under daylight (Supplementary Movie 2). The steady-state excitation and emission spectra of the xerogels and complexes are shown in Fig. 2b and Fig. 2c, respectively. Both the maximum excitation wavelength (max) and maximum emission wavelength (max) of PAM-TD complexes are redshifted compared with the corresponding PAM-X xerogels, and they gradually redshift with increasing annealing temperature. The delayed excitation and emission spectra of the xerogels and complexes are shown in Fig. 2d and 2e, respectively. PAM-X exhibits a max at 458 nm, while PAM-X exhibits a redshifted max of 478 nm. Both max and max of the PAM-TD complexes also redshift with increasing annealing temperature. Specifically, PAM-TD , PAM-TD , and PAM-TD exhibit max at 366 nm, 370 nm, and 370 nm, and max at 488 nm, 491 nm, and 494 nm, respectively. Notably, the steady-state spectra of PAM-TD and PAM-TD exhibit multiple emission centres. In addition to the peak at 404 nm, shoulder peaks appear at 455 nm and 494 nm (Fig. 2c), coinciding with the phosphorescence spectra (Fig. 2e) and indicating strong phosphorescent contributions. The PAM-TD complexes exhibit weaker excitation-dependent emission (EDE) characteristics than the PAM-X xerogels, and PAM-TD exhibits nearly negligible EDE, especially in the delayed spectra (Supplementary Fig. 3 and 4).

The phosphorescence lifetimes of PAM-X and PAM-X are 155.7 ms and 322.5 ms, respectively (Fig. 2f). The phosphorescence lifetime of PAM-TD is only 208.1 ms, whereas that of PAM-TD reaches up to 622.5 ms. Similarly, PAM-X exhibits a total QY of 4.2% and a phosphorescence QY of only 0.6%, while PAM-X shows significantly increased total and phosphorescence QYs of 14.3% and 4.7%, respectively. The total and phosphorescence QYs of PAM-TD are only 3.1% Iand 1.2%, but they reach 26.8% and 17.6% for PAM-TD , respectively, (Fig. 2g). It is worth mentioning that the phosphorescence performance of PAM-TD , which simultaneously features a long RTP lifetime and a high QY, outperforms most previously reported NTL-based UOP material systems (Supplementary Table 1), and its phosphorescence QY is the largest among the reported polymer NTLs (Supplementary Fig. 5A).

Note that the DES (TD) does not exhibit intrinsic phosphorescence. To further study the effect of DES, hydrogels and xerogels containing only one of the components (TBAB or DBPA) were also prepared (Supplementary Methods), and they are named as PAM-T , PAM-T , PAM-T , PAM-D , PAM-D and PAM-D , respectively. PAM-D shows a more homogeneous structure than PAM-T (Supplementary Fig. 6). The delayed excitation and emission spectra and phosphorescence lifetime profiles of the gels are provided in Supplementary Fig. 7 and 8. The max of PAM-T , PAM-T and PAM-T are 374 nm, 454 nm and 476 nm, and those of PAM-D , PAM-D and PAM-D are 430 nm, 488 nm and 492 nm, respectively. In addition, the RTP lifetimes of the PAM-DBPA gels are generally longer than those of the corresponding PAM-TBAB gels. Noticeably, the max and RTP lifetimes of the PAM-TBAB and PAM-DBPA gels are also significantly larger or longer than those of the corresponding PAM gels. These results suggest that both TBAB and DBPA are effective in enhancing the RTP properties of PAM gels, and DBPA is more effective than TBAB. Note that the max and RTP lifetimes of the PAM-TBAB and PAM-DBPA gels are still smaller or shorter than those of the corresponding PAM-TD complexes, which in turn proves that the cooperative effects of TBAB and DBPA lead to the excellent RTP behaviors of the complexes. Therefore, the introduction of TBAB and DBPA into the PAM gel through solvent exchange and wet annealing at an elevated temperature both contribute to the redshifted PL emissions, higher QYs, and longer phosphorescence lifetimes for the complexes.

Reversible and environmentally stable HTP behaviors

Surprisingly, PAM-TD exhibits eminent HTP performance. It shows San afterglow visible to naked eyes for 2 s even at 393 K (Fig. 2h, Supplementary Movie 3). As the temperature rises, the phosphorescence intensity gradually decreases and the lifetime shortens slightly. From 293 K to 393 K, the maximum phosphorescence intensity decreases by 78.3% (Fig. 2i), but the lifetime shortens by only 41.1%, remaining 366.2 ms at 393 K (Fig. 2j). The phosphorescence emission of PAM-TD becomEes negligible until the temperature is more than 418 K (145C) (Supplementary Fig. 9a). Such excellent HTP has never been reported in NTLs. The phosphorescence emission gradually recovers during the cooling process (Supplementary Fig. 9b), indicating the reversibility of HTP performance. The phosphorescence behaviors of the PAM-TD complex after different heating-cooling cycles were also tested. The PAM-TD complex was heated to 90C and then cooled to room temperature in a nitrogen atmosphere. The RTP lifetimes after 5, 20, and 50 cycles are 612.5 ms, 587.8 ms and 581.6 ms, respectively (Supplementary Fig. 10), slightly lower than that of the original PAM-TD (622.5 ms), demonstrating the stability and reversibility of this PAM-TD complex. Interestingly, as the temperature increases from 313 K to 373 K, both afterglow time and phosphorescence intensity decrease almost linearly (Supplementary Fig. 11), and this linear relationship remains stable after a heating-cooling cycle (Supplementary Fig. 12).

The PAM-TD complex also exhibits similar HTP in organic solvents like DMSO (Supplementary Fig. 13) and long-term solvent-resistant RTP (Supplementary Fig. 14). Moreover, it also exhibits excellent environmental stability, showing RTP and HTP behaviours similar to the original sample after being heated at 100C in a nitrogen atmosphere or in DMSO (Supplementary Movies 4 and 5).

Microstructures and interactions

The transmittance of the samples changes dramatically (Fig. 3a, Supplementary Fig. 15). The xerogels demonstrate high transparency up to 99.7%, whereas that of the complexes decreases to 40.7% for PAM-TD and then gradually increases with increasing wet annealing temperature to 88.9% for PAM-TD (Fig. 3b). The tensile mechanical properties of the gels are dramatically enhanced after the treatments (Supplementary Fig. 16). The tensile strength (σ ) and elastic modulus (E) of PAM-TD are as high as 55.7 MPa and 168.1 MPa, both are hundreds or thousands times of those of the PAM-H hydrogel, whose σ and E are only 0.41 MPa and 0.15 MPa, respectively. Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) measurements show that the glass transition temperatures (T ) of the complexes Egradually rise with the increasing annealing temperatures, from about 80C for PAM-TD to 102C for PAM-TD (Supplementary Fig. 17 and 18).

The dramatic change in the physical properties indicates the significantly enhanced interactions in the complexes after the DES solvent exchange and wet annealing treatments. The formation of interactions between PAM and DES during the wet annealing process is indirectly proven by dissolution experiments, as AM is difficult to dissolve in DES at room temperature but can be fully dissolved within 0.5 h at 90C (Supplementary Fig. 19).

The change in the interactions leads to the change in their microstructures. SEM investigation shows that PAM-X has a conventional uniform porous structure (Supplementary Fig. 20a, b), while PAM-TD exhibits a dense layered structure (Fig. 3c, Supplementary Fig. 20c, d), and PAM-TD exhibits denser layered and wrinkled structures (Fig. 3d, Supplementary Fig. 20e, f). Wide-angle X-ray diffraction (WXRD) profiles show that both PAM-TD and PAM-X have only one similar broad diffraction peak (Supplementary Fig. 21a) but no crystalline diffraction peaks of TBAB and DBPA (Supplementary Fig. 21b, c), suggesting the amorphous structures of the complexes and the uniform dispersion of DES within them. Small-angle X-ray scattering (SAXS) was performed to reveal structural transformations below 100 nm in the complexes. Both PAM-TD and PAM-TD exhibit isotropic 2D SAXS patterns (Fig. 3e, Supplementary Fig. 22). Moreover, in the low q area (< 0.3 nm-1), both complexes exhibit scattering power-law exponents close to -4 (Fig. 3f), indicating spherical dense structures with clear phase separation interfaces. Note that the scattering intensity of PAM-TD in the low q range is lower than that of PAM-TD , suggesting that wet annealing leads to reduced aggregation at the 100 nm scale in PAM-TD . As q increases, the SAXS profile of PAM-TD aligns with that of PAM-TD , confirming similar aggregation morphologies at smaller scales in them52.

Spatial electron density fluctuations in the complexes were analyzed using the Debye-Bueche model:
𝐼(𝑞) = 𝐼0 / (1+𝑞2𝜉2)2 (1)
where ξ represents the characteristic length of density fluctuations. In weak phase separation systems, density fluctuations are localized, resulting in a relatively small ξ. Macroscopic phase separation typically involves a long-range increase in ξ. For PAM-TD , ξ is 14.05 nm, while wet annealing reduces ξ to 9.86 nm for PAM-TD , reflecting reduced phase separation.

Hydrogen bonding is the dominant interaction in the gels and complexes. FTIR was performed to investigate the hydrogen bonding interactions between the components (Fig. 3g). The formation of DES is verified by the presence of all characteristic absorption bands of TBAB and DBPA as well as the shift of the stretching vibration band of carbonyl groups in DBPA from 1715 cm-1 to 1732 cm-1 in the DES53. The presence of multiple absorption bands of carbonyl groups in 1675-1740 cm-1 in the complexes confirms the incorporation of DES in them. The absorption band of -NH shifts from 3410 cm⁻¹ in IPAM-X to 3355 cm-1 in PAM-TD and further to 3336 cm-1 in PAM-TD , and the C=O stretching vibration band at 1658 cm-1 in PAM-X shifts to 1651 cm-1 in PAM-TD , indicating that both solvent exchange and wet annealing lead to the formation of stronger hydrogen bonding in the complexes.

Low-field nuclear magnetic resonance hydrogen spectroscopy (LF-1H NMR) was performed to analyze the transformation of hydrogen bonding in the gels and complexes. A larger T indicates stronger hydrogen bond constraints and reduced mobility54. Protons with a higher T are more detectable than those with a lower T . In gels, water molecules are present in different bonding states, and the related T of protons are: free water (> 10 ms), moderately restricted water (1-10 ms) and highly restricted water (< 1 ms) (Fig. 3h). Note that a trace amount of water is still present in the PAM-TD complexes. The percentages of the three types of protons in PAM-H, PAM-TD and PAM-TD were calculated from the spectra and are shown in Fig. 3i. In PAM-H, most water is moderately restricted (87.8%) and a small fraction is free (5.7%, T in the range of 100-1000 ms). Compared with PAM-H, PAM-TD shows a significantly increased percentage of highly restricted protons (77.6%) but a decreased portion of moderately restricted protons (16.6%) with an increased T (~ 400-1000 ms). The possible reason is that the solvent exchange with DES leads to the breakage of weak hydrogen bonds between bound water and PAM and hence the formation of free water that is subsequently removed from the complex, leaving the strongly bonded water. In PAM-TD , the percentage of highly restricted protons decreases to 45.9%, but that of moderately restricted protons increases to 26.7%, and very surprisingly, the percentage of high-mobility protons increases to 27.3%, and T extends to 2000 ms, approaching the ultra-free water level. These results suggest that part of the water molecules hydrogen-bonded to PAM are transformed into super-free water, possibly due to the formation of strong hydrogen bonds between DES and PAM.

The macroscopic and microscopic characterizations reveal that both DES solvent exchange and wet annealing significantly alter the aggregation structures and interactions in the PAM-TD complexes. DES solvent exchange leads to the aggregation of PAM chains and the formation of stronger interactions among them, which induces large-sized phase separation of PAM-TD and a decreased transmittance. The formation of strong hydrogen bonding between PAM and DES during wet annealing partially disrupts self-aggregation of PAM chains, leading to a transformation from large aggregates into smaller structures and hence the increase in transparency of the complexes.

Theoretical calculations were also performed to understand the interactions between the components. The hydrogen bonding energies of DES (TD), PAM-PAM and PAM-DES are calculated to be 160.79, 237.61, and 264.22 kJ mol-1, respectively (Supplementary Fig. 23), suggesting that DES is not easy to form hydrogen bonding with PAM during the solvent exchange process. However, wet annealing at an elevated temperature is favorable for the breakage of the original hydrogen bonding and thereafter the formation of new and stronger hydrogen bonding between DES and PAM. This is verified by interaction region indicator (IRI) analysis which simulates the molecular conformations of annealed PAM-TD and PAM-X . The calculation results show that TBAB forms hydrogen bonds with PAM via bromide anions, and larger interaction potential surfaces are formed between PAM and DES than between PAM and PAM (Fig. 4a).

RTP and HTP mechanisms

The above experimental and theoretical results all confirm the transformation of microstructures and the formation of strong hydrogen bonding during the solvent exchange and wet annealing processes. This is the main reason for the dramatically enhanced and redshifted PL emissions of the PAM-TD complexes. For the PAM xerogels, drying process leads to the removal of water, and hence the close contact of amide groups and the formation of hydrogen bonds among PAM chains. For the PAM-TD complexes, the solvent exchange and wet annealing treatments also lead to the removal of water, and hence the close contact of amide groups and the formation of strong hydrogen bonding among PAM chains and between PAM and DES. Both PAM xerogels and PAM-TD complexes exhibit dramatically enhanced fluorescence emissions than the PAM hydrogel. The reason is that the hydrogen bonding is effective in rigidifying the molecule conformations and hence inhibiting non-radiative transitions. The PAM xerogels and PAM-TD complexes also exhibit redshifted fluorescence emissions than the PAM hydrogel. The reason is that the close contact of amide groups, which are typical NCCs, leads to the formation extended TSC and hence reduced energy gaps between ground and excited states. The PAM-TD complexes exhibit more redshifted fluorescence emissions than the corresponding PAM xerogels. The reason is the formation of more and stronger hydrogen bonding between DES and PAM and hence the formation of more extended TSC.

The experimental results prove that the introduction of DES into the PAM gel through solvent exchange and wet annealing at an elevated temperature is essential to the RTP emissions of the complexes. To further understand the origin of phosphorescence emission, spin-orbit coupling (SOC) constants (ξ) of the PAM-DES complexes and PAM xerogels were calculated. In the PAM-TD complex, using three repeating units of PAM, one TBAB molecule and one DBPA molecule as the model (Fig. 4b), the energy gaps between S and T , T , and T are very small (< 0.3 eV), easily facilitating ISC. Notably, ξ(S , T ), ξ(S , T ), ξ(S , T ), and ξ(S , T ) are very large, with ξ(S , T ) reaching 1005.91 cm-1, confirming that PAM-TD undergoes efficient ISC to generate triplet excitons. On the contrary, the PAM xerogel exhibits low ξ (Fig. 4d). In addition, natural transition orbital (NTO) simulations show that the highest occupied natural transition orbital (HONTO) is concentrated on the bromide anions of TBAB, part of PAM, and interaction zones, while the lowest unoccupied natural transition orbital (LUNTO) is mainly distributed on DBPA, verifying electron transfer between PAM and DES (Fig. 4c). These theoretical calculation results well explained the easier occurrence of RTP of the PAM-DES complexes than the PAM gels.

The PAM-TD complexes, especially those prepared at elevated temperatures, exhibit redshifted PL emissions, higher QYs, and longer phosphorescence lifetimes than the corresponding PAM xerogels, suggesting that wet annealing plays important roles in the RTP emission of the PAM-TD complexes. Wet annealing leads to the redissolution of PAM and establishes strong PAM-DES interactions, leading to the high SOC and ISC efficiency, therefore promoting phosphorescence generation and enhancing phosphorescence QYs. On the other hand, the formation of strong hydrogen bonding between PAM and DES leads to more extended TSC and rigidified molecular conformations, and hence the redshifted and significantly prolonged RTP emissions.

HTP performances of organic materials based on TLs are generally explained with the rigid structures of the systems and their stability at high temperatures25,27,28,55,56. The significantly higher T of PAM-TD than other complexes and xerogels suggests its high rigidity, and this is the reason for its excellent HTP. Here we performed thermogravimetric analysis (TGA), in-situ variable-temperature SAXS and FTIR experiments and theoretical calculations to further confirm the structure stability of PAM-TD .

The DES (TD), PAM xerogel and PAM-TD complexes are all stable at temperatures below 150C (Supplementary Fig. 24). The more significant mass loss in the 150-250C temperature range of PAM-TD than PAM-TD can be attributed to the evaporation of free DES that is not hydrogen bonded with PAM. Upon heating up to 150C, the 2D SAXS patterns of PAMA-TD show almost equally sized dispersion rings (Fig. 5a). The 1D profiles almost completely coincide as the temperature increases, with only slight decrease in the scattering intensity in the low q region (< 0.3 nm-1), and very slight increase in the high q region (> 0.3 nm-1) (Fig. 5b, and Supplementary Fig. 25a). The Porod plots derived from the 1D SAXS profiles are nearly smooth in the high q region (Supplementary Fig. 25b), and the calculated correlation length (ξ) only slightly increases from 11.8 Å at 40C to about 12.9 Å at 150C (Fig. 5c). In addition, the average radius of gyration (R ) of the polymer chain in the low q region, calculated from the Guinier plot (Supplementary Fig. 25c), decreases by 2.03 nm when heated from 40C to 150C (Fig. 5d). These results confirm that the structure of PAM-TD remains compact during the heating process, with only very slight structural loosening.

The in-situ variable-temperature ATR-FTIR spectra of PAM-TD and PAM-TD were obtained (Fig. 5e, g). In the temperature range of 30C to 150C, the absorption bands attributed to the alkyl and carbonyl groups of PAM remains nearly no change, consistent with the results of SAXS, confirming the long-range structural stability of the PAM-DES complexes at high temperatures. However, obvious differences are observed in the intensity and wavenumber of the amino absorption band of PAM-TD and PAM-TD (Fig. 5f, h). For PAM-TD , the intensity of amino group decreases slightly with temperature till 60°C and then drops significantly, and the absorption wavenumber blueshifts from 3329 cm⁻¹ (30°C) to 3339 cm⁻¹ (60°C), but it gradually redshifts to 3315 cm-1 at 90°C and 3304 cm-1 at 150°C. For PAM-TD , the intensity and wavenumber of the amino absorption band change very slightly with increasing temperature till 120°C (Fig. 5i, j), confirming that the chemical structure and hydrogen bonding in PAM-TD are very stable below 120°C, and this is the reason for the phenomenon that PAM-TD still has a RTP lifetime of 366.2 ms at 120°C. A more significant change in the intensity and wavenumber of the amino absorption band of PAM-TD is observed when the temperature reaches 150C, suggesting the breakage of hydrogen bonding interactions in it. This is the reason for the disappearance of phosphorescence emission at 145°C. Note that the wavenumbers of the absorption band of amino groups in PAM-TD above 90°C are very close to those of PAM-TD , verifying the feasibility of using 90°C to anneal PAM-TD .

Shermo calculations were used to simulate the thermodynamic parameter changes of DES (TD), PAM-PAM and PAM-TD clusters during the heating process. The internal energy (U) and enthalpy (H) of the three systems all decrease gradually with increasing temperature (Supplementary Fig. 26). Their Gibbs free energy (G) also decreases with increasing temperature (Fig. 5k-m). The decreased percentage of G of PAM-TD is only about 12.79% when the temperature rises from 20°C to 150°C, lower than those of PAM-PAM and especially DES (TD) (Fig. 5n). This again indicates the interactions between PAM and DES are very stable and not strongly affected by temperature.

Therefore, the fragile interactions between PAM and DES caused by solvent exchange were enhanced after high-temperature annealing, and hydrogen bonds exhibit good thermal stability, enabling HTP in PAM-TD (Fig. 5o).

Universality of the strategy

Other PAM complexes were also prepared by using different DESs. The DESs include TBAB and 3-bromopropionic acid (shortened as TBAB-BPA), TBAB and 2-bromoethanol (TBAB-BMT), choline chloride and 2,3-dibromopropionic acid (CHCl-DBPA), CHCl and methylurea (CHCl-MU). And the corresponding complexes are named as PAM-TBAB-BPA, PAM-TBAB-BMT, PAM-CHCl-DBPA, and PAM-CHCl-MU, respectively. The complexes all exhibit persistent RTP emissions (Supplementary Fig. 27). The maxof phosphorescence of PAM-TBAB-BPA, PAM-TBAB-BMT, and PAM-CHCl-DBPA are 495 nm, 482 nm, and 489 nm, respectively, which are red-shifted than that of the PAM xerogels, while that of PAM-CHCl-MU is 472 nm, close to that of PAM-X . The phosphorescence lifetimes of PAM-TBAB-BPA, PAM-TBAB-BMT, and PAM-CHCl-DBPA are 564.2 ms, 513.7 ms, and 608.4 ms, respectively, while only 169.3 ms for PAM-CHCl-MU (Supplementary Fig. 28). In addition, PAM-TBAB-BPA and PAM-TBAB-BMT have high total QYs (~ 20%) and phosphorescence QYs (>10%), whereas PAM-CHCl-DBPA has a lower total Q Y and a phosphorescence QY of 8.24% and 5.9%, respectively. Notably, PAM-CHCl-MU has a high total QY of 21.1% but a low phosphorescence QY of 4.9% (Supplementary Fig. 29).

Obviously, the complexes prepared with the DESs containing neutral bromo groups (CHCl-DBPA) or bromide ions (TBAB-BPA and PAM-TBAB-BMT) all exhibit larger max, longer phosphorescence lifetimes and the higher phosphorescence QYs than the complex prepared with the DES without any bromine atoms (CHCl-MU), suggesting that the heavy atom effect of bromine element contributes significantly to the excellent phosphorescence properties of the PAM complexes. It is necessary to mention that some other structural factors of the DES should affect the interactions and compatibility between the polymer and DES and hence the PL behaviours of the complexes. For example, we selected tetramethylammonium bromide (TMAB, with a smaller steric hindrance and stronger hydrophilicity than TBAB) and DBPA with a molar ratio of 1:1 to form a DES (TMAB-DBPA, named as TMD), and prepared PAM-TMD using the same methods described in this work. The prompt and delayed max of PAM-TMD (Supplementary Fig. 30) are both red-shifted compared with those of PAM-TD (Fig. 2c, e), but the RTP lifetime of PAM-TMD (411.8 ms) is shorter than that of PAM-TD (622.5 ms).

Phosphorescent complexes can also be prepared by using some other non-aromatic polymers. Polyacrylic acid (PAA) xerogel (PAA-X), and PAA-TD complex were prepared by using the same preparation methods as those for the PAM gels, and their photophysical properties are shown in Supplementary Fig. 31. The prompt and delayed max of PAA-X are 444 nm and 482 nm, and those of PAA-TD are 490 nm and 542 nm, respectively, suggesting that the DES solvent exchange and wet annealing are also very effective in red-shifting the emissions of PAA. PAA-X and PAA-TD exhibit significantly red-shifted prompt and delayed emissions than corresponding PAM-X and PAM-TD , suggesting that using some other polymers like PAA can achieve more red-shifted prompt and delayed emissions than PAM. Unfortunately, PAA-TD only exhibits a short RTP lifetime of 32.3 ms, which is much shorter than that of PAA-X (415 ms). The possible reason is that the interactions between DES and PAA in PAA-TD are not as strong as those in PAA-X.

Applications of time- and temperature-dual-responsive information encryption

The ultralong phosphorescence lifetimes and the differences in the PL intensities and lifetimes of the complexes prepared at different wet annealing temperatures enable the advanced encryption and anti-counterfeiting applications of the complexes. For example, as shown in Fig. 6, a pattern with the digits "8888" is constructed with PAM-TD and PAM-TD complex strips, in which the information of "2025" is constructed with the PAM-TD complex strips. Under daylight and UV irradiation, only the pattern "8888" is shown. Immediately after turning off the UV light, the pattern "8888" is still visible, but a faint "2025" message can be observed due to the brighter phosphorescence emission of PAM-TD . After 6 s, the afterglow of PAM-TD completely disappears, leaving clear information of "2025". After 9 s, the information becomes nearly invisible, since the phosphorescence of PAM-TD also fades, realizing the time-encrypted information storage. Moreover, temperature can be employed to realize "burn after reading" information encryption. The information "2025" is clear at 50C, but it fades dramatically at 90C. After heating at 90C and cooling to room temperature, which simulates the annealing process and hence the change of PAM-TD into PAM-TD , only the pattern "8888" is shown no matter under or after the UV irradiation, achieving the permanent damage of the encrypted information "2025".

Methods
Materials

Acrylamide (AM, 99%), acrylTic acid (AA, 99%), tetrabutylammonium bromide (TBAB, 99%), tetramethylammonium bromide (TMAB, 99%), 2,3-dibromopropionic acid (DBPA, 99%), 3-bromopropionic acid (BPA, 99%), 2-bromoethanol (BMT, 98%), and methylurea (MU, 99%) were purchased from Shanghai Macklin Biochemical Technology Co., Ltd (Shanghai, China); choline chloride (CHCl, 99%) and potassium persulfate (KPS, 99%) were from Beijing Innochem Technology Co., Ltd (Beijing, China). Unless specified, all chemicals were of A.R.

Purification

TBAB was dissolved in water, and then was precipitated in a mixed solvent of ether and ethanol (V : V = 3:2). The dissolution-precipitation process was repeated three times. DBPA were recrystallized for three times in a mixed solvent of ethanol: water (V : V = 3: 1). The precipitates and crystals were vacuum dried for 48 h.

Preparation of DESs, PAM hydrogel, complexes and xerogels

The DESs of TBAB-DBPA, TBAB-BPA, TMAB-DBPA, TBAB-BMT, CHCl-DBPA, and CHCl-MU, were prepared by mixing the two components with a moalr ratio of 1:1 and then heating at 90C under stirring until uniform and transparent liquids were formed. The purely hydrogen-bonding crosslinked PAM hydrogel was synthesized via free-radical polymerization of AM without using any chemical crosslinkers. Specifically, 15 g of acrylamide (AM) was dissolved in 20 g of deionized water under stirring at room temperature in nitrogen atmosphere (flow rate: 40 mL min-1). Then, KPS (0.5 wt % of AM) was added as an initiator. The solution was ultrasonicated for 15 min, and the sonication power was 120 W. Then filled into a mold made of two glass plates and a silicone spacer. After heating at 60℃ for 6 h, a PAM hydrogel with a water content of 57 wt % was obtained.

The hydrogel was subjected to solvent exchange in an excess of ETBAB-DBPA (TD) DES for 48 h to ensure complete solvent exchange, with the solvent replaced every 12 h, yielding PAM-TD . Subsequently, annealing was performed at 60C and 90C for 1.5 h in nitrogen atm osphere (flow rate: 50 mL min-1) to obtain PAM-TD and PAM-TD , respectively. The complexes were dried in a vacuum oven for 24 h and stored for later use. The original PAM hydrogel was dried to a water content of 10 wt% (similar to the liquid content of the complexes) to obtain a PAM-H hydrogel or completely dried in a vacuum oven at room temperature to obtain a PAM xerogel (PAM-X), which was then annealed in a vacuum oven for 1.5 h to obtain PAM-X . Other complexes, including PAM-TBAB-BPA, PAM-TBAAB-BMT, PAM-TMAB-DBPA, PAM-CHCl-DBPA, and PAM-CHCl-MU, were also prepared in the same way.

Photoluminescence Spectroscopy

The prompt and delayed spectra (delay time: 1 ms), photoluminescence lifetimes and quantum yields at room temperature and high temperature were measured by FLS-980 fluorescence spectrometer (Edinburgh Instruments, UK). Photographs and movies of the complex samples under and after the irradiation of lights were taken with Vivo X90 Pro cell phone (Vivo, China) using professional mode in a dark room and photographs of delayed emissions were taken after turning off the light for 0.1 s. The ISO is set to 1/2000 and the shutter speed is set to 1/15 s.

Measurement of liquid contents

The liquid contents of complex samples were calculated using the following equation:
𝐿𝑖𝑞𝑢𝑖𝑑 𝑐𝑜𝑛𝑡𝑒𝑛𝑡 = (𝑚 −𝑚 ) / 𝑚 ×100 % (2)
where m is the mass of the hydrogels or complexes sample and m is the mass of the corresponding xerogel sample. Their average values and deviations were calculated.

Characterization

UV-vis absorption spectra were measured using Perkin Elmer LAMBDA 1S050 + UV/vis/NIR spectrophotometer. Wide Angle X-ray Diffraction (WXRD) measurements were performed on samples ground into powders with Brooke D8 Advance (Bruker Corporation, USA), scanning speed R of 5 min-1. Scanning Electron Microscopy (SEM) was performed on freeze-dried samples with Hitachi HIT ACHI SU8010 (Hitachi, Japan). Small Angle X-ray Scattering (SAXS) was performed with Anton paar Saxsess MC2 (Anton paar Corporation, Austria). Fourier transform infrared (FTIR) spectra of the samples were recorded with a Nicolet 50 spectrometer (Thermo Electron Corporation, USA), and the number of sCcans was 32 at a resolution of 1 cm−1. All samples were tested by the potassium bromide pellet method. Low-Field Nuclear Magnetic Resonance (LF-NMR) was performed with MesoMR 12-060 H-I (Neway Electronic Technology Co., Ltd, China). The main frequency of the instrument is 12 MHz, the diameter of the probe coil is 25 mm, and the test temperature is 32C. In-situ variable-temperature SAXS data were tested by Xeuss 3.0 (Xenocs, France) (Copper target: X-ray tube power 30W, focal spot diameter: 30um; Detector: Eiger2R 1M). A Bruker Tensor 27 spectrometer (Bruker Tensor, German) was used to measure the in-situ variable-temperature FT-IR spectra of samples.

Theoretical calculation

All the electronic structures and energy levels of these compounds were calculated with Gaussian 09 (version D.01) using B3LYP density functional theory and 6-31G (d,p) basis. Energy calculations for the first excited singlet state were carried out using time-dependent density functional theory (TD-DFT)57. The dispersion effect was corrected by Grimme's DFT-D358,59. Chemical bonds and weak interactions in chemical systems were calculated by interaction region indicator (IRI) method. The spin-orbit coupling (SOC) matrix elements between singlet and triplet states was evaluated through ORCA (version 5.0.0)60. Natural transition orbitals (NTOs) and interaction region indicator (IRI) analysis plots61 were determined using Multifwn software (version 3.8)60. Molecular and electron clouds were created using VMD software (version 1.9.4)62. Thermodynamic data were calculated using the Shermo program63.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In this manuscript, Wang and coworkers report the development of a novel type of photoluminescent eutectogels with ultralong room-temperature and high-temperature phosphorescence and the detailed studies of their microstructures and photoluminescence mechanism. They employed solvent exchange and wet annealing methods to transform a polyacrylamide (PAM) hydrogel into a eutectogel. The solvent change with a bromine-containing deep eutectic solvent (DES) and wet annealing treatments both lead to dramatic changes in the interactions and hence the photoluminescence behaviors of the gels. The resulting eutectogels exhibit outstanding room-temperature phosphorescence (RTP) and high-termperature phosphorescence (HTP), with RTP lifetimes up to 622.5 ms and a HTP lifetime of 366.2 ms even at 120 °C. This work also provides the example of direct participation of DESs in phosphorescence emission. In summary, this work presents a significant advance in the development of non-aromatic ultralong organic phosphorescent (UOP) materials that do not rely on traditional phosphors, and hence this work is of great scientific and practical significance. Therefore, the publication of the manuscript in Nature Communications is recommended after some minor revisions.\n1. A purely hydrogen-bonding crosslinked PAM hydrogel was used in this work. Why was the PAM hydrogel chosen and any requirements for the structure of the hydrogel, e.g., functional groups, solid content and crosslinking density? In addition, the reasons for choosing other experimental conditions like solvent exchange time and annealing time are better to be described.\n2. Different non-aromatic DESs were used to prove the universality of this photoluminescent eutectogel preparation strategy, and the reported eutectogels all exhibit RTP emission. I am curious that, except PAM, if some other polymers can also be used.\n3. I understand that, to emphasize the non-aromatic nature of this eutectogel system, the polymer and DESs used in this work do not contain any aromatic phosphors. It would be interesting to know what will happen when polymers and DESs with aromatic phosphors are used.\n4. To understand the contribution of the DESs on the photoluminescence of the eutectogels, it is suggested to carry out comparative studies on samples prepared with the two individual components of the DES, i.e., tetrabutylammonium bromide and 2,3-dibromopropionic acid, respectively.\n5. The eutectogel shows high-temperature phosphorescence. My question is that does the eutectogel after the heating and cooling processes shows the same RTP and HTP behaviors as those of the original eutectogel.\n6. The texts in some figures (e.g. the inset in Figure 3f) are difficult to perceive clearly. The quality of the figures should be improved.\n7. The manuscript contains a few grammatical errors, and its fluency can be further improved.", "reviewer_2": "This study presents a novel nonaromatic eutectogel exhibiting ultralong room-temperature phosphorescence (RTP), prepared from a polyacrylamide hydrogel through solvent exchange with a bromine-containing deep eutectic solvent followed by wet annealing. The resulting material demonstrates an exceptionally long RTP afterglow of up to 9.5 s, a lifetime of up to 622.5 ms, and remarkably, high-temperature phosphorescence (HTP) at 120 ℃ with a lifetime of 366.2 ms—the first reported instance of HTP in nontraditional luminogens. The enhanced performance is attributed to the heavy-atom effect of the DES and rigidification via hydrogen bonding. The eutectogel enables advanced time- and temperature-dual-responsive information encryption. Thus, I would recommend the immediate acceptance of this paper after addressing the following issues.\n1. The text contains inconsistent terminology and spelling errors that need to be standardized to avoid ambiguity. The term is inconsistently used, appearing as both \"eutectogels\" and \"eutetogels\", and should be unified.\n2. Although FTIR and LF-NMR confirmed the formation of strong hydrogen bonds between DES and PAM, the dynamic evolution of these interactions during the \"solvent exchange-wet annealing\" process remains unclear. Key experimental evidence should be supplemented, such as providing comparative FTIR spectra at different solvent exchange durations to illustrate changes in hydrogen bonding strength over time and validate the rationality of the 48-hour exchange period.\n3. Critical parameters are missing in the description of PAM hydrogel synthesis, compromising experimental reproducibility: while \"15 min of sonication\" is mentioned, the sonication power was not specified. This parameter significantly affects monomer dissolution and bubble removal, thereby influencing hydrogel uniformity. Additionally, the nitrogen flow rate was not indicated for the wet annealing process, although a \"nitrogen atmosphere\" was referenced.\n4. Although control groups such as PAM-H and PAM-X were included, the rationale for selecting PAM-H with 10 wt% water content as a control was not justified. Supplementary data comparing the RTP performance of PAM hydrogels with different water contents should be provided to verify the scientific basis for selecting the 10 wt% condition.\n5.The study demonstrates the use of PAM eutectogels in time–temperature dual-responsive information encryption but lacks essential validation for practical application. Environmental stability tests should be supplemented.\n6.The dimensions of the molecular models used in calculations (e.g., the number of repeating units in the PAM chain, the number of DES molecules) were not specified, which may raise doubts about the reliability of the computational results.\n7. HTP was only tested from 293 K to 393 K. The phosphorescence decay behavior at higher temperatures remains unexplored, leaving the upper-temperature limit of HTP undetermined. Moreover, although a nearly linear decrease in afterglow duration and intensity was reported between 313 K and 373 K, performance recovery after thermal cycling was not tested, making it difficult to confirm the reversibility of the HTP properties.\n8.The performance of the PAM eutectogels was presented in isolation without comparison with previously reported NTL-based UOP materials or DES-based photofunctional materials, making it difficult to highlight the advantages of this study.\n9.There are some grammatical errors in the manuscript, authors should check them carefully.", "reviewer_3": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts.", "reviewer_4": "In this manuscript entitled \"Nonaromatic Eutectogels with Ultralong Room-temperature and High-temperature Phosphorescence\", Zhong et al. report the fabrication of a novel type of pure organic phosphorescent materials through a simple solvent change treatment of a polyacrylamide (PAM) hydrogel with a non-aromatic bromine-containing deep eutectic solvent (DES) followed by wet annealing at an elevated temperature. The obtained eutectogels exhibit long room-temperature phosphorescence of 622.5 ms and excellent high-temperature resistance. To my best knowledge, this is the first report of phosphorescent eutectogels whose phosphorescence emissions do not rely on traditional phosphors, signifying a new area in the development of novel DES containing materials. Moreover, the authors also provided a convincing explanation of the photoluminescence mechanism through very detailed structural characterizations and theoretical calculations. I do believe that the significant novelty and potential applications of this work meet the high standards of Nature Communications. Therefore, the publication of this manuscript is strongly recommended. The authors need to address the following issues to refine the manuscript.\n1. The Experimental part. Some experimental parameters, such as the delay time of the phosphorescence spectrum, the camera parameters for taking pictures, should be provided.\n2. The author should explain the reason for choosing polyacrylamide (PAM) as the eutectogel matrix rather than other polymers. And do the eutectogels involving other common polymers such as polyacrylic acid (PAA) also have outstanding phosphorescent properties?\n3. It is not rigorous and reasonable for the authors to merely change different types of DES and conclude that ionic bromine may enhance phosphorescence performance Theoretically, covalent bromine can significantly enhance intersystem crossing, while the role of ionic bromine is different (Aggregate, 2021, 2, 13). It is suggested to modify the description in the manuscript and further discuss which factor leads to the significant improvement of phosphorescence performance of eutectogels.\n4. Generally speaking, the introduction of heavy atoms, although it helps to promote phosphorescence in the system and increase the quantum yield, inevitably shortens the phosphorescence lifetime. But, in this work, the phosphorescence lifetime of the eutectogel is prolonged. The current manuscript is still somewhat vague in the explanation of the mechanism. It is suggested that the authors separately describe the role of different steps in the strategy in simultaneously achieving the improvement of phosphorescence lifetime and quantum yield.\n5. The author explained that the interactions between DES and the polymer main chain affect the phosphorescence properties of the system. It is well known that acrylamide is highly hydrophilic, and the DES used in this work contains tetrabutylammonium bromide, a highly hydrophobic component with large steric hindrance, which aggravates the aggregation of the polyacrylamide main chain during the solvent exchange process. If a DES containing heavy atoms with better compatibility with the acrylamide unit is used, could more DES be introduced to enhance the phosphorescence performance of the system?\n6. A similar strategy has been reported to enhance the mechanical properties of polyvinyl alcohol (PVA) eutectogels. The related references are better to be cited and elaborate on the similarities and differences of such strategies in polyacrylamide (PAM) gels."}, "author_response": "Point-by-point Response to Reviews’ Comments\nWe sincerely thank the editor and all reviewers for your time and effort in evaluating our\nmanuscript. We greatly appreciate the constructive and insightful comments provided, which\nare invaluable in helping us improve the quality and clarity of our work. We have carefully\nconsidered each comment from the editor and reviewers and have made substantial\nrevisions to the manuscript accordingly.\nBelow, we provide point-by-point responses to all comments raised, with corresponding\nchanges highlighted in the revised manuscript and Supplementary Materials. For clarity and\nease of review, we have used the following formatting conventions in this response document:\nour responses to the reviewers' comments are presented in blue text, while all revisions made\nin the manuscript and Supplementary Information are highlighted in yellow. We hope this\nformatting will facilitate the review process and make it easier to track the changes we have\nmade in response to the valuable feedback.\nWe believe that these revisions have significantly strengthened the manuscript, and we hope\nthat the revised version now meets the standards for publication in Nature Communications.\nWe thank you in advance for your consideration of our revised manuscript.\nReviewer #1\nIn this manuscript, Wang and coworkers report the development of a novel type of\nphotoluminescent eutectogels with ultralong room-temperature and high-temperature\nphosphorescence and the detailed studies of their microstructures and photoluminescence\nmechanism. They employed solvent exchange and wet annealing methods to transform a\npolyacrylamide (PAM) hydrogel into a eutectogel. The solvent change with a bromine-\ncontaining deep eutectic solvent (DES) and wet annealing treatments both lead to dramatic\nchanges in the interactions and hence the photoluminescence behaviors of the gels. The\nresulting eutectogels exhibit outstanding room-temperature phosphorescence (RTP) and high-\ntemperature phosphorescence (HTP), with RTP lifetimes up to 622.5 ms and a HTP lifetime of\n366.2 ms even at 120C. This work also provides the example of direct participation of DESs\nin phosphorescence emission. In summary, this work presents a significant advance in the\ndevelopment of non-aromatic ultralong organic phosphorescent (UOP) materials that do not\nrely on traditional phosphors, and hence this work is of great scientific and practical\nsignificance. Therefore, the publication of the manuscript in Nature Communications is\nrecommended after some minor revisions.\nResponse: Many thanks for your kind comments on the feature of our work and your very\nconstructive and insightful suggestions.\n1. A purely hydrogen-bonding crosslinked PAM hydrogel was used in this work. Why was the\nPAM hydrogel chosen and any requirements for the structure of the hydrogel, e.g., functional\ngroups, solid content and crosslinking density? In addition, the reasons for choosing other\nexperimental conditions like solvent exchange time and annealing time are better to be\ndescribed.\nResponse:\n1. The reasons for choosing a purely hydrogen-bonding crosslinked PAM hydrogel are as\nfollows: 1) PAM is a kind of polymer without any aromatic structures, which provides a\nprerequisite for us to construct a non-aromatic phosphorescent system. The PAM hydrogel\nused in this work was prepared by thermally initiated free-radical polymerization of AM\n(using KPS as the initiator) without using any chemical crosslinkers, avoiding the\nintroduction of other aromatic luminescent molecules. 2) PAM has been found to exhibit\nintrinsic fluorescence and RTP emissions in solid state and in some highly crosslinked\nhydrogels, since the clustering of amide groups enables efficient through-space\nconjugation (TSC) and the presence of abundant O and N atoms facilitates the occurrence\nof inter-system crossing (ISC) between singlet and triplet states. By studying the\ndifferences in the photoluminescence (PL) behaviors, structures as well as the interactions\nbetween the PAM eutectogels and the pure PAM xerogel, it is possible to understand how\nthe deep eutectic solvents (DESs) affect the PL behaviors especially the phosphorescence\nemissions of the eutectogels.\n2. The requirements on the structure of the hydrogels may include: 1) The polymer should\ncontain functional groups that function as nonconventional chromophores; 2) The polymer\nshould contain functional groups that can form strong hydrogen bonding with the\ncomponents of DESs; 3) The polymer should have poor solubility in the DESs, enabling\nthe aggregation of the polymer chains during solvent exchange and the reformation of\nstrong interactions with deep eutectic solvents (DESs) after annealing; 4) The solid content\nof the hydrogel and the cross-linking degree of the hydrogel should be moderate, since a\nhigh solid content and a high cross-linking degree makes it difficult for the introduction of\nDESs into the hydrogel during solvent exchange and the formation of strong interactions\nbetween DESs and the polymer matrix, and, on the contrary, a low solid content and a low\ncross-linking degree makes it impossible for the formation of a hydrogel through pure\nhydrogen bonding.\n3. The reasons for choosing the solvent exchange time of 48 h include: 1) The solvent\nexchange time was determined on the basis of the weight change of the gel. We found that\nthe weight of the gel remained constant after 24 h solvent exchange. Solvent exchange\ntime was chosen to be 48 h to ensure the complete solvent exchange. 2) We prepared PAM-\nTD gel samples with different DES solvent exchange time (0.5 h, 1 h, 2 h, 4 h, 6 h, 12 h,\n24 h, 36 h and 48 h) and tested their FTIR spectra (Supplementary Fig. 1a). We analyzed\nthe changes in the characteristic peak positions of the amino groups and carbonyl groups\nin PAM as well as the carboxyl groups in DES. From 0.5 h to 24 h, the -N-H absorption\nband gradually broadens and red-shifts (Supplementary Fig. 1b), and the C=O stretching\nvibration band also significantly red-shifts (Supplementary Fig. 1c), indicating the\nformation of more and stronger hydrogen bonds in the gels. Notably, after 4 h of solvent\nexchange, a stretching vibration peak of carboxylic acid appears at 1700-1750 cm-1 and\ngradually red-shifts till 24 h, confirming the successful introduction of DES. However, the\nred-shift of all characteristic absorption bands becomes not obvious when the solvent\nexchange time is more than 24 h, suggesting the completion of solvent exchange. The\nabove experimental results further confirm the rationale of the 48 h solvent exchange time.\na\n0.5 h\nn (N-H)\nn (C=O)\n1 h\n2 h\ne\nc 4 h\nn\na\nmitt\n6 h\ns\nn\na 12 h\nr\nT\n24 h\n36 h\n48 h\n4000 3500 3000 2500 2000 1500 1000\nWavenumber (cm-1)\nb c\n1 h 0.5 h n (N-H) 1 h 0.5 h n (C=O)\n2 h\n2 h\n4 h\n4 h\n6 h\ne e\nc 6 h c\na n a n 12 h\nmitt 12 h mitt 24 h\nn s 24 h n s\na a 36 h\nTr 36 h Tr\n48 h\n48 h\n3500 3400 3300 3200 3100 3000 1800 1750 1700 1650 1600 1550 1500\nWavenumber (cm-1) Wavenumber (cm-1)\nSupplementary Fig. 1. FTIR spectra of PAM-TD gels prepared with different solvent\nexchange durations.\n4. The reasons for choosing the annealing time of 1.5 h include: 1) Through previous\nexperiments (Supplementary Fig. 18), we found that AM and DESs could form a\ntransparent and uniform liquid at 90C within 30 min. 2) Additionally, we found that no\nbetter phosphorescent performance could be achieved in the eutectogels with longer\nannealing times.\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nIntroduction Section, the last paragraph: A purely hydrogen-bonding cross-linked\npolyacrylamide (PAM) hydrogel was used as the gel matrix, since PAM is a non-aromatic\npolymer exhibiting intrinsic fluorescence and RTP emissions in solid state and in some\nhydrogels.\nResults Section, Preparation and photophysical properties of eutectogels, paragraph 1: A\npurely hydrogen-bonding crosslinked PAM hydrogel was synthesized via free-radical\npolymerization of acrylamide (AM) without using any chemical crosslinkers to ensure that no\naromatic components were introduced into the system. Then it was immersed in an excess DES\ncomposed of tetrabutylammonium bromide (TBAB) and 2,3-dibromopropionic acid (DBPA)\n(shortened as TD) at room temperature for 48 h to obtain a PAM-TD eutectogel.\nThe\nRT\ncompletion of solvent exchange is confirmed with the facts of no weight change of the gel and\nno red-shifts of all characteristic absorption bands of PAM and TD in the FTIR spectra of the\ngels after 24 h solvent exchange (Supplementary Fig. 1).\nSupplementary Information:\nSupplementary Figures: Supplementary Fig. 1 and the related texts are provided.\n2. Different non-aromatic DESs were used to prove the universality of this photoluminescent\neutectogel preparation strategy, and the reported eutectogels all exhibit RTP emission. I am\ncurious that, except PAM, if some other polymers can also be used.\nResponse: We agree with your comment that some other polymers can also be used. We have\nprepared polyacrylic acid (PAA) hydrogel, PAA-X xerogel and PAA-TD eutectogel using the\n90\nsame preparation methods as those for the PAM gels.\nThe photophysical properties PAA-X xerogel and PAA-TD eutectogel were measured and\n90\nshown in Supplementary Fig. 27. The prompt and delayed max of PAA-X are 444 nm and\nem\n482 nm (Supplementary Fig. 27a, b), and those of PAA-TD are 490 nm and 542 nm,\n90\nrespectively (Supplementary Fig. 27d, e), suggesting that the DES solvent exchange and wet\nannealing are also very effective in red-shifting the emissions of PAA. For comparison, the\nprompt and delayed max of PAM-X are 369 nm and 458 nm, and those of PAM-TD are\nem 90\n404 nm and 494 nm, respectively. Obviously, PAA-X and PAA-TD exhibit significantly red-\n90\nshifted prompt and delayed emissions than corresponding PAM-X and PAM-TD , suggesting\n90\nthat using some other polymers like PAA can achieve more red-shifted prompt and delayed\nemissions than PAM.\nUnfortunately, PAA-TD only exhibits a short RTP lifetime of 32.3 ms (Supplementary Fig.\n90\n27f), which is much shorter than that of PAA-X (415 ms) (Supplementary Fig. 27c).\nThe\npossible reason is that the interactions between DES and PAA in PAA-TD are not as strong\n90\nas those in PAA-X.\nWe will continue exploring polymer systems suitable for this strategy and developing different\ntypes of eutectogels in the subsequent experiments.\n(a) (b) (c)104\ne n\nsit y 444 E E x m\ne n\nsit y 482 E E x m\n103\n415  P ms\nnt nt\nd\nP L I\nd\nP L I\no\nu nt s 102\ne e C\nz z\nm\nali\nm\nali\n101\nor or\nN N\n100\n300 400 500 600 700 300 400 500 600 700 0 100 200 300 400\nWavelength (nm) Wavelength (nm) Time (ms)\n(d\nnt e n\nsit y ) 490 E E x m (e\nnt e n\nsit y ) 542 E E x m (f)\n1\n1\n0\n0\n3\n4 32.3  P ms\nd\nP L I\nd\nP L I\no\nu nt s 102\ne e C\nm\nali z\nm\nali z\n101\nor or\nN N\n100\n300 400 500 600 700 300 400 500 600 700 0 100 200 300 400\nWavelength (nm) Wavelength (nm) Time (ms)\nSupplementary Fig. 27. Photophysical properties of the PAA-X xerogel and PAA-TD\n90\neutectogel. (a, b) Prompt (a) and delayed (delay time = 1 ms) (b) excitation and emission spectra\nof PAA-X under the corresponding max and max. (c) Phosphorescence lifetime decay\nem ex\nprofiles of PAA-X. (d, e) Prompt (d) and delayed © excitation and emission spectra of PAA-\nTD under the corresponding max and max . © Phosphorescence lifetime decay\n90 em ex\nprofiles of PAA-TD .\nManuscript:\nResults Section, Universality of the strategy. The following paragraph has been added.\nPhosphorescent eutectogels can also be prepared by using some other non-aromatic polymers.\nPolyacrylic acid (PAA) xerogel (PAA-X) and PAA-TD eutectogel were prepared by using\n90\nthe same preparation methods as those for the PAM gels, and their photophysical properties\nare shown in Supplementary Fig. 27. The prompt and delayed max of PAA-X are 444 nm\nem\nand 482 nm, and those of PAA-TD are 490 nm and 542 nm, respectively, suggesting that the\nof PAA. PAA-X and PAA-TD exhibit significantly red-shifted prompt and delayed emissions\n90\nthan corresponding PAM-X and PAM-TD , suggesting that using some other polymers like\nPAA-TD only exhibits a short RTP lifetime of 32.3 ms, which is much shorter than that of\nTD are not as strong as those in PAA-X.\nMethods Section: Preparation of PAA, PAA-X and PAA-TD gels\n90\neutectogel are the same as those for the corresponding PAM gels. In brief, a PAA hydrogel\nwith a water content of 57 wt % was prepared with free-radical polymerization method, then it\nwas subjected to solvent exchange in an excess of TBAB-DBPA (TD) DES for 48 h to obtain\nan eutectogel PAM-TD , followed by annealing at 90C for 1.5 h, obtaining a PAM-TD\nRT 90\neutectogel. A PAA-X xerogel was obtained by complete drying of the PAA hydrogel in a\nnitrogen atmoshpere.\nSupplementary Figures: Supplementary Fig. 27 is added.\n3. I understand that, to emphasize the non-aromatic nature of this eutectogel system, the\npolymer and DESs used in this work do not contain any aromatic phosphors. It would be\ninteresting to know what will happen when polymers and DESs with aromatic phosphors are\nused.\nResponse: We do believe that some polymers and DESs containing aromatic phosphors may\nprovide more interesting photoluminescent properties, which is of great significance for\nenriching luminescent materials. We will carry out the studies in the near future.\n4. To understand the contribution of the DESs on the photoluminescence of the eutectogels, it\nis suggested to carry out comparative studies on samples prepared with the two individual\ncomponents of the DES, i.e., tetrabutylammonium bromide and 2,3-dibromopropionic acid,\nrespectively.\nResponse: Thank you for your valuable suggestion.\nThe eutectogels in this system contains two components, which interact with each other and\nalso with the PAM chains. These interactions are all in a competitive relationship. Following\nyour suggestion, we prepared the hydrogels containing only one of the components (TBAB or\nDBPA), respectively, and studied their PL behaviors.\nThe DES (TD) content of the previously prepared eutectogel was approximately 10% (mass\nfraction), and TBAB and DBPA were in an equal molar ratio (1:1). To ensure the same molar\nratio of the individual DES component in the gels, the hydrogels were prepared with the\nfollowing feeding ratios: 3g AM, 0.1743g TBAB (or 0.1257 g DBPA), and 0.03g KPS, which\nwere dissolved in 4g of deionized water. The hydrogel preparation method was the same as that\nfor the PAM hydrogel. The resulting PAM-TBAB and PAM-DBPA hydrogels are denoted as\nPAM-T and PAM-D , respectively. They were vacuum dried for 72 h at room temperature to\nH H\nconstant weights, obtaining xerogels denoted as PAM-T and PAM-D . Finally, PAM-T\nRT RT 90\nand PAM-D were obtained by annealing the xerogels at 90C for 1.5 h in a nitrogen\n90\natmosphere.\nThe PAM-TBAB gels show obvious structural inhomogeneity, and the PAM-T and PAM-T\nH RT 90\ngels are opaque (Supplementary Fig. 5a), with several large white crystal-like structures in the\ngels. Note that the originally solution was transparent and uniform. So, it is speculated that the\npolymerization of AM led to a sharp decrease in the solubility of TBAB in water (similar to the\ncrystallization of crown ethers, J. Am. Chem. Soc., 2023, 145, 3763-3773), causing the\ncrystallization and precipitation of TBAB. For the PAM-DBPA gels, PAM-T and PAM-T\nH RT\nare transparent while PAM-T turns opaque (Supplementary Fig. 5b).\nH\nT (b), PAM-T (c), PAM-D (d), PAM-D © and PAM-D (f).\nX 90 H X 90\nPAM-T does not exhibit obvious RTP visible to naked eyes, but PAM-T and PAM-T show\nH RT 90\nvisible phosphorescence. The delayed spectra of the gels are shown in Supplementary Fig. 6a-\nc. PAM-T exhibits a max at 374 nm, while PAM-T and PAM-T exhibits a max of 454\nH em RT 90 em\nnm and 476 nm, respectively. The phosphorescence lifetime of PAM-T is only 9.2 ms, while\nH\nthose of PAM-T and PAM-T reaches up to 297.8 ms and 532.1 ms, respectively\nRT 90\n(Supplementary Fig. 6d).\n(a) (b)\ny Em y Em\nsit sit\nn n\ne e\nnt nt\nd\nI\nd\nI\ne e\nz z\nali ali\nm m\no r o r\nN N\n300 360 420 480 540 600 300 350 400 450 500 550 600\nWavelength (nm) Wavelength (nm)\n(c) (d) 104\nP\ny Em\nsit PAM-T H 9.2 ms\nnt e n 103 P P A A M M - - T T X 90 5 2 3 9 2 7 . . 1 8 m m s s\nd\nI\nnt\ns\ne u102\nz o\nali C\nm\no r 101\nN\n100\n250 300 350 400 450 500 550 600 0 1 2 3 4\nWavelength (nm) Time (s)\nSupplementary Fig. 6 Photophysical properties of the PAM-TBAB gels. (a-c) Delayed\nexcitation and emission spectra of PAM-T (a), PAM-T (b) and PAM-T (c) under the\nH X 90\ncorresponding max and max (delay time = 1 ms). (d) Phosphorescence lifetime decay\nem ex\nprofiles.\nPAM-D , PAM-D and PAM-D all show visible phosphorescence at room temperature. The\nH X X90\ndelayed spectra and phosphorescence lifetime decay profiles of the gels are shown in\nSupplementary Fig. 7. PAM-D exhibits a max at 430 nm, while PAM-D and PAM-D\nH em X 90\nexhibits a max of 488 nm and 492 nm, respectively. Interesting, the emission peak shapes\nem\nand max of PAM-D and PAM-D are almost exactly the same as those of PAM-TD and\nem X X90 RT\nPAM-TD respectively (Fig. 2e), indicating that PAM and DBPA have a stronger interaction\n90\nin the eutectogel.\nThe phosphorescence lifetime of PAM-D is 42.7 ms, while those of PAM-D and PAM-D\nH X X90\nreaches up to 307.8 ms and 559.3 ms, respectively (Supplementary Fig. 7d). The RTP lifetimes\nof PAM-DBPA gels are generally longer than those of the corresponding PAM-TBAB gels.\n(a) (b)\ny Em y Em\nsit sit\nn n\ne e\nnt nt\nd\nI\nd\nI\ne e\nz z\nali ali\nm m\no r o r\nN N\n300 350 450 500 550 600 300 350 400 450 500 550 600 650\nWavelength (nm) Wavelength (nm)\n(c) (d) 104\nP\ny Em PAM-D 42.7 ms\nsit\nPAM-D\nH\n307.8 ms\nn 103 X\ne PAM-D 559.3 ms\nnt 90\nd\nI\nnt\ns\ne u102\nz o\nali C\nm\no r 101\nN\n100\n300 350 400 450 500 550 600 650 0 1 2 3 4\nWavelength (nm) Time (s)\nSupplementary Fig. 7. Photophysical properties of the PAM-DBPA gels. (a-c) Delayed\nexcitation and emission spectra of PAM-D (a), PAM-D (b) and PAM-D (c) under the\nH X 90\ncorresponding max and max (delay time = 1 ms). (d) Phosphorescence lifetime decay\nem ex\nprofiles.\nObviously, the RTP lifetimes of the PAM-TBAB and PAM- DBPA gels are significantly longer\nthan those of the corresponding PAM gels, suggesting that both TBAB and DBPA are effective\nin enhancing the RTP properties of the PAM gels, and DBPA is even more effective than TBAB.\nOn the other hand, the RTP lifetimes of the PAM-TBAB and PAM- DBPA gels are shorter than\nthat of the corresponding PAM-TD eutectogels, suggesting that the cooperative effects of\nTBAB and DBPA lead to the excellent RTP behaviors of the eutectogels.\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nResults Section, Preparation and photophysical properties of eutectogels: To further study\nthe effect of DES, hydrogels and xerogels containing only one of the components (TBAB or\nDBPA) were also prepared (Supplementary Methods), and they are named as PAM-T , PAM-\nH\nT , PAM-T , PAM-D , PAM-D and PAM-D , respectively. PAM-D shows a more\nX 90 H X 90 H\nhomogeneous structure than PAM-T (Supplementary Fig. 5). The delayed excitation and\nH\nemission spectra and phosphorescence lifetime decay profiles of the gels are provided in\nSupplementary Fig. 6 and 7. The max of PAM-T , PAM-T and PAM-T are 374 nm, 454\nem H X 90\nnm and 476 nm, and those of PAM-D , PAM-D and PAM-D are 430 nm, 488 nm and 492\nH X 90\nnm, respectively. In addition, the RTP lifetimes of the PAM-DBPA gels are generally longer\nthan those of the corresponding PAM-TBAB gels. Noticeably, the max and RTP lifetimes of\nem\nthe PAM-TBAB and PAM-DBPA gels are also significantly larger or longer than those of the\ncorresponding PAM gels. These results suggest that both TBAB and DBPA are effective in\nenhancing the RTP properties of PAM gels, and DBPA is more effective than TBAB. Note that\nthe max and RTP lifetimes of the PAM-TBAB and PAM-DBPA gels are still smaller or\nem\nshorter than those of the corresponding PAM-TD eutectogels, which in turn proves that the\ncooperative effects of TBAB and DBPA lead to the excellent RTP behaviors of the eutectogels.\nTherefore, the introduction of TBAB and DBPA into the PAM gel through solvent exchange\nand wet annealing at an elevated temperature both contribute to the redshifted PL emissions,\nhigher QYs, and longer phosphorescence lifetimes for the eutectogels.\nSupplementary Information:\nSupplementary methods: Preparation of PAM-TBAB and PAM-DBPA gels\nHydrogels and xerogels containing only one of the DES components (i.e., TBAB or DBPA)\nwere prepared. The feeding ratio of the raw materials were as follows: 3g AM, 0.1743g TBAB\n(or 0.1257 g DBPA), and 0.03g KPS, which were dissolved in 4g of deionized water. The\nhydrogel preparation method was the same as that for the PAM hydrogel. The resulting PAM-\nTBAB and PAM-DBPA hydrogels are denoted as PAM-T and PAM-D , respectively. They\nH H\nwere vacuum dried at room temperature for 72 h to constant weights, obtaining xerogels\ndenoted as PAM-T and PAM-D . Finally, PAM-T and PAM-D were obtained by annealing\nX X 90 90\nthe xerogels at 90C for 1.5 h in a nitrogen atmosphere.\nSupplementary Figures: Supplementary Fig. 5-7 and the related texts are provided.\n5. The eutectogel shows high-temperature phosphorescence. My question is that does the\neutectogel after the heating and cooling processes shows the same RTP and HTP behaviors as\nthose of the original eutectogel.\nResponse:\nFollowing your suggestion, we measured the RTP and HTP behaviors of the PAM-TD\n90\neutectogel after heating-cooling treatment in a nitrogen atmosphere. The PAM-TD eutectogel\n90\nwas heated to 90C and then cooled to room temperature. The HTP behavior of PAM-TD\n90\nafter one heating-cooling cycle was tested. From 293 K to 393 K, the phosphorescence intensity\ndecreases by 75.6% (Supplementary Fig. 9a), similar to the original PAM-TD . The RTP\n90\nlifetimes after 5, 20, and 50 heating-cooling cycles are 612.5 ms, 587.8 ms and 581.6 ms,\nrespectively (Supplementary Fig. 9b), slightly lower than that of the original PAM-TD (622.5\n90\nms), demonstrating the stability and reversibility of this PAM-TD eutectogel.\n90\n(a)3.0\n393K\n(b)104\nCycles  P\n5 ) 373K 5 612.5 ms\n02.5\n1 353K 20 587.8 ms\n× 333K 103 50 581.6 ms\nu., 2.0 313K\ny (\na.\n1.5\n293K\nu\nnt\ns\n102\nsit\nC\no\nn1.0\ne\nnt 101\nL\nI0.5\nP\n0.0 100\n425 450 475 500 525 550 575 600 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0\nWavelength (nm) Time (s)\nSupplementary Fig. 9. (a) Temperature-dependent delayed emission spectra of PAM-TD\n90\nafter one heating-cooling cycle (max= 365 nm). (b) Phosphorescence lifetime decay profiles\nex\nand the lifetimes of PAM-TD after different heating-cooling cycles in a nitrogen atmosphere\n90\n(293-393 K).\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nResults Section, HTP and solvent-resistant phosphorescence: The phosphorescence\nbehaviors of the PAM-TD eutectogel after different heating-cooling cycles were also tested.\n90\natmosphere. The RTP lifetimes after 5, 20, and 50 cycles are 612.5 ms, 587.8 ms and 581.6 ms,\nrespectively (Supplementary Fig. 9), slightly lower than that of the original PAM-TD (622.5\n90\nms).\nSupplementary Information:\nSupplementary Figures: Supplementary Fig. 9 has been added.\n6. The texts in some figure (e.g. the inset in Fig. 3f) are difficult to perceive clearly. The quality\nof the figures should be improved.\nResponse: We are very sorry for the poor quality of the figures. We have improved the quality\nof the figures, including but not limited to the illustration in Fig. 3f.\n7. The manuscript contains a few grammatical errors, and its fluency can be further improved.\nResponse: We have carefully checked and corrected the grammatical errors and the\nexpressions. The revised parts have been marked in the manuscript.\nReviewer #2\nThis study presents a novel nonaromatic eutectogel exhibiting ultralong room-temperature\nphosphorescence (RTP), prepared from a polyacrylamide hydrogel through solvent exchange\nwith a bromine-containing deep eutectic solvent followed by wet annealing. The resulting\nmaterial demonstrates an exceptionally long RTP afterglow of up to 9.5 s, a lifetime of up to\n622.5 ms, and remarkably, high-temperature phosphorescence (HTP) at 120 ℃ with a lifetime\nof 366.2 ms—the first reported instance of HTP in nontraditional luminogens. The enhanced\nperformance is attributed to the heavy-atom effect of the DES and rigidification via hydrogen\nbonding. The eutectogel enables advanced time- and temperature-dual-responsive information\nencryption. Thus, I would recommend the immediate acceptance of this paper after addressing\nthe following issues.\nResponse: Many thanks for your kind comments on the feature of our work and your very\nconstructive and insightful suggestions.\n1. The text contains inconsistent terminology and spelling errors that need to be standardized\nto avoid ambiguity. The term is inconsistently used, appearing as both \"eutectogels\" and\n\"eutetogels\", and should be unified.\nResponse: We are very sorry for the inconsistent terminology and spelling errors.\nThe terms \"eutectogels\" and \"eutetogels\" have been unified as \"eutectogels\".\n2. Although FTIR and LF-NMR confirmed the formation of strong hydrogen bonds between\nDES and PAM, the dynamic evolution of these interactions during the \"solvent exchange-wet\nannealing\" process remains unclear. Key experimental evidence should be supplemented, such\nas providing comparative FTIR spectra at different solvent exchange durations to illustrate\nchanges in hydrogen bonding strength over time and validate the rationality of the 48-hour\nexchange period.\nResponse: Thank you for your suggestion.\nWe determined 48 h as the solvent exchange time based on the fact that the gel weights remain\nconstant after 24 h solvent exchange.\nFollowing your suggestion, we prepared PAM-TD gel samples with different DES solvent\nexchange time (0.5 h, 1 h, 2 h, 4 h, 6 h, 12 h, 24 h, 36 h and 48 h) and tested their FTIR spectra\n(Supplementary Fig. 1a). We analyzed the changes in the characteristic peak positions of the\namino groups and carbonyl groups in PAM as well as the carboxyl groups in DES. From 0.5 h\nto 24 h, the -N-H absorption band gradually broadens and red-shifts (Supplementary Fig. 1b),\nand the C=O stretching vibration band also significantly red-shifts (Supplementary Fig. 1c),\nindicating the formation of more and stronger hydrogen bonds in the gels. Notably, after 4 h of\nsolvent exchange, a stretching vibration peak of carboxylic acid appears at 1700-1750 cm-1 and\ngradually red-shifts till 24 h, confirming the successful introduction of DES. However, the red-\nshift of all characteristic absorption bands becomes not obvious when the solvent exchange\ntime is more than 24 h, suggesting the completion of solvent exchange. The above experimental\nresults further confirm the rationale of the 48 h solvent exchange time.\na\n0.5 h\nn (N-H)\nn (C=O)\n1 h\n2 h\ne\nc 4 h\nn\na\nmitt\n6 h\ns\nn\na 12 h\nr\nT\n24 h\n36 h\n48 h\n4000 3500 3000 2500 2000 1500 1000\nWavenumber (cm-1)\nb c\n1 h 0.5 h n (N-H) 1 h 0.5 h n (C=O)\n2 h\n2 h\n4 h\n4 h\n6 h\ne e\nc 6 h c\na n a n 12 h\nmitt 12 h mitt 24 h\nn s 24 h n s\na a 36 h\nTr 36 h Tr\n48 h\n48 h\n3500 3400 3300 3200 3100 3000 1800 1750 1700 1650 1600 1550 1500\nWavenumber (cm-1) Wavenumber (cm-1)\nSupplementary Fig. 1. FTIR spectra of PAM-TD gels prepared with different solvent\nexchange durations.\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nResults Section, Preparation and photophysical properties of eutectogels: The completion\nof solvent exchange is confirmed with the facts of no weight change of the gel and no red-shifts\nof all characteristic absorption bands of PAM and TD in the FTIR spectra of the gels after 24\nh solvent exchange (Supplementary Fig. 1).\nSupplementary Information:\nSupplementary Figures: Supplementary Fig. 1 and the related texts are provided.\n3. Critical parameters are missing in the description of PAM hydrogel synthesis, compromising\nexperimental reproducibility: while \"15 min of sonication\" is mentioned, the sonication power\nwas not specified. This parameter significantly affects monomer dissolution and bubble\nremoval, thereby influencing hydrogel uniformity. Additionally, the nitrogen flow rate was not\nindicated for the wet annealing process, although a \"nitrogen atmosphere\" was referenced.\nResponse: We are sorry for not providing some critical experimental parameters. The\ninformation has been provided in the revised manuscript. The sonication power was 120 W,\nthe flow rates of nitrogen used during the AM dissolution and wet annealing of eutectogels\nwere 40 mL/min and 50 mL/min, respectively.\n4. Although control groups such as PAM-H and PAM-X were included, the rationale for\nselecting PAM-H with 10 wt% water content as a control was not justified. Supplementary data\ncomparing the RTP performance of PAM hydrogels with different water contents should be\nprovided to verify the scientific basis for selecting the 10 wt% condition.\nResponse: The reason why we chose the PAM-H hydrogel with 10 wt% water content as the\ncontrol is that the liquid contents of PAM-TD , PAM-TD and PAM-TD are 11.27 wt%,\nRT 60 90\n10.52 wt%, and 9.87 wt%, respectively. Therefore, we selected a hydrogel with a similar liquid\ncontent as the control.\nFollowing your suggestion, we tested the phosphorescence emission spectra (Supplementary\nFig. 2a) and corresponding RTP lifetimes (Supplementary Fig. 2b) of the PAM hydrogels with\ndifferent water contents, ranging from the highest water content (57 wt%) of the initial hydrogel\nto about 6 wt% of the dried hydrogel containing almost only bound water.\n(a) (b) 104\ny 474 Water 57% Water contents \nsit Content 50% 57% 7.2 P ms\nnt e n 4 3\n2\n0 0\n0\n% %\n%\n103 5 4 0 0 % % 2 9 7 .8 .2 m m s s\nL I 10% 30% 53.7 ms\nd\nP 6%\nu\nnt s\n102\n2\n1\n0\n0\n%\n%\n7\n9\n9\n6\n.\n.\n3\n9\nm\nm\ns\ns\ne o 6% 119.7 ms\nali z C\nm\nr 101\no\nN\n100\n350 400 450 500 550 600 0 200 400 600 800 1000\nWavelength (nm) Time (ms)\nSupplementary Fig. 2. RTP performance of PAM hydrogels with different water contents. (a)\nDelayed emission spectra under the corresponding max (delay time = 1 ms). (b)\nex\nPhosphorescence lifetime decay profiles.\nObviously, as the water content gradually decreases from 57 wt% to 6 wt%, the max\nem\ngradually red-shifts, and the RTP lifetimes gradually increases from 8 ms to 119.7 ms. Note\nthat the max of the hydrogel with 6 wt% water content is almost the same as that of PAM-X\nem\n(Fig. 2e), but the RTP lifetime is still lower than that of PAM-X (155.7 ms).\nTo minimize the effect of water (or liquid) content on the photoluminescence (PL) of the gels,\na PAM-H hydrogel with a liquid content similar to the PAM-TD eutectogels was prepared by\ndrying the initial PAM hydrogel to 10 wt% water content at ambient conditions.\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nResult Section. Preparation and photophysical properties of eutectogels: The water content\nof the original PAM hydrogel is 57 wt%, while the liquid contents of PAM-TD , PAM-TD ,\nRT 60\nand PAM-TD are 11.27 wt%, 10.52 wt%, and 9.87 wt%, respectively. To minimize the effect\n90\nof water (or liquid) content on the photoluminescence (PL) of the gels (Supplementary Fig. 2),\na PAM-H hydrogel with a liquid content similar to that of the PAM-TD eutectogels was\nprepared by drying the initial PAM hydrogel to 10 wt% water content at ambient conditions.\nSupplementary Information:\nSupplementary Figures: Supplementary Fig. 2 has been provided.\n5. The study demonstrates the use of PAM eutectogels in time-temperature dual-responsive\ninformation encryption but lacks essential validation for practical application. Environmental\nstability tests should be supplemented.\nResponse:\nFollowing your suggestion, we tested the environmental stability of phosphorescence behavior\nof the eutectogels.\nWe tested the thermal stability of the PAM-TD eutectogel in a nitrogen environment. After\n90\nbeing continuously heated at 100C for 3 days, the afterglow was still visible to the naked eye\nfor nearly 8 seconds when the temperature was restored to room temperature (Supplementary\nMovie 4).\nWe also immersed PAM-TD in DMSO and heated it at 100C for 24 h. It still shows obvious\ntemperature solvent stability.\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nResult Section. HTP and solvent-resistant phosphorescence: Moreover, it also exhibits\nexcellent environmental stability, showing RTP and HTP behaviours similar to the original\nsample after being heated at 100C in a nitrogen atmosphere or in DMSO (Supplementary\nMovies 4 and 5).\nSupplementary Information:\nSupplementary Movies: Supplementary Movies 4 and 5 are provided.\n6. The dimensions of the molecular models used in calculations (e.g., the number of repeating\nunits in the PAM chain, the number of DES molecules) were not specified, which may raise\ndoubts about the reliability of the computational results.\nResponse: The model includes three repeating units of PAM, one TBAB molecule and one\nDBPA molecule.\nRevisions in the Manuscript:\nTitle of Fig. 4: The model includes three repeating units of PAM, one TBAB molecule and one\nDBPA molecule.\n7. HTP was only tested from 293 K to 393 K. The phosphorescence decay behavior at higher\ntemperatures remains unexplored, leaving the upper-temperature limit of HTP undetermined.\nMoreover, although a nearly linear decrease in afterglow duration and intensity was reported\nbetween 313 K and 373 K, performance recovery after thermal cycling was not tested, making\nit difficult to confirm the reversibility of the HTP properties.\nResponse:\nFollowing your suggestion, we measured the phosphorescence behaviors of PAM-TD in a\n90\nwide temperature range from 293 K to 428 K. It was found that the phosphorescence emission\npeak becomes negligible till the temperature is more than 418 K (Supplementary Fig. 8a),\ndetermining the upper-temperature limit of HTP.\n(a)3.0 (b)1.8\nTemperature 293K Temperature RT\n5 ) 1 02.5 3 3 1 3 3 3 K K 5 ) 1 01.5 3 3 1 3 3 3 K K\n× 353K × 353K\nu., 2.0 Heating 373K u., 1.2 Cooling 373K\na. 393K a. 393K\nsit y\n(1.5 4\n4\n4\n1\n1\n2\n3\n8\nK\nK\nsit y\n(0.9 4\n4\n4\n0\n1\n1\n3\n3\nK\nK\ne\nn1.0\n428K e\nn0.6\n423K\nnt nt\nL\nI\n0.5 L\nI\n0.3\nP P\n0.0 0.0\n450 500 550 600 650 450 500 550 600 650\nWavelength (nm) Wavelength (nm)\nSupplementary Fig. 8. The HTP reversibility of PAM-TD . Temperature-dependent delayed\n90\nemission spectra during heating (a) and cooling (b) processes (delay time: 1 ms).\nThe phosphorescence emission gradually recovers during the cooling process (Supplementary\nFig. 8b), indicating the reversibility of HTP performance. The phosphorescence behaviors of\nthe PAM-TD eutectogel after different heating-cooling cycles were also tested in a nitrogen\n90\natmosphere. The PAM-TD gel was heated to 90C and then cooled to room temperature. The\n(Supplementary Fig. 9), slightly lower than that of the original PAM-TD (622.5 ms).\n90\n(a)3.0\n393K\n(b)104\nCycles  P\n5 ) 373K 5 612.5 ms\n02.5\n1 353K 20 587.8 ms\n× 333K 103 50 581.6 ms\nu., 2.0 313K\ny (\na.\n1.5\n293K\nu\nnt\ns\n102\nsit\nC\no\nn1.0\ne\nnt 101\nL\nI0.5\nP\n0.0 100\n425 450 475 500 525 550 575 600 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0\nWavelength (nm) Time (s)\nSupplementary Fig. 9. (a) Temperature-dependent delayed emission spectra of PAM-TD\n90\nafter one heating-cooling cycle (max= 365 nm). (b) Phosphorescence lifetime decay profiles\nex\nand the lifetimes of PAM-TD after different heating-cooling cycles (293-393 K).\n90\ncycle (293 K - 393 K) are measured (Supplementary Fig. 9a). A linear relationship between the\nphosphorescence intensity and temperature in the range of 313 K to 373 K is also observed\n(Supplementary Fig. 11), further confirming the reversibility and practicality of HTP\nperformance.\n3.0\n)\n5\n02.5\n1\n×\nu.,\na.2.0\n(\ny\nsit\nn\ne1.5\nnt\ns.\ni\nh\no1.0\nP\n0.5\n293 313 333 353 373 393\nTemperature (K)\nSupplementary Fig. 11. The variation of phosphorescence intensity with increasing\ntemperature of PAM-TD after one heating-cooling cycle (293-393 K).\nManuscript:\nResults Section, HTP and solvent-resistant phosphorescence: The phosphorescence\nemission of PAM-TD becomes negligible until the temperature is more than 418 K (145C)\n90\n(Supplementary Fig. 8a). Such excellent HTP has never been reported in NTLs. The\nphosphorescence emission gradually recovers during the cooling process (Supplementary Fig.\n8b), indicating the reversibility of HTP performance. The phosphorescence behaviors of the\nPAM-TD eutectogel after different heating-cooling cycles were also tested. The PAM-TD\n90 90\ngel was heated to 90C and then cooled to room temperature in a nitrogen atmosphere. The\nRTP lifetimes after 5, 20, and 50 cycles are 612.5 ms, 587.8 ms and 581.6 ms, respectively\n(Supplementary Fig. 9), slightly lower than that of the original PAM-TD (622.5 ms),\n90\ndemonstrating the stability and reversibility of this PAM-TD eutectogel. Interestingly, as the\n90\ntemperature increases from 313 K to 373 K, both afterglow time and phosphorescence intensity\ndecrease almost linearly (Supplementary Fig. 10), and this linear relationship remains stable\nafter a heating-cooling cycle (Supplementary Fig. 11).\nSupplementary Information:\nSupplementary Figures: Supplementary Figs. 8, 9 and 11 have been added.\n8. The performance of the PAM eutectogels was presented in isolation without comparison\nwith previously reported NTL-based UOP materials or DES-based photofunctional materials,\nmaking it difficult to highlight the advantages of this study.\nResponse:\nWe have cited some of the relevant literatures on DES-based luminescent materials in the\nmanuscript, and summarized the phosphorescence performance of some UOP materials based\non NTLs in Supplementary Table 1.\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nIntroduction Section: replacing “But photoluminescent eutectogels remain unexplored until\nvery recently, and they mostly only exhibit fluorescence emissions based on TLs incorporated\ninto them46-48.” with “However, photoluminescent eutectogels remain largely unexplored until\nvery recently, and they mostly only exhibit fluorescence emissions. In 2023, Criado et al.\naccidentally found that a eutectogel based on a benzotriazolinone-modified glutamic acid\nderivative shows excellent electrical conductivity and fluorescence emission47. Later, Zhang et\nal. developed a eutectogel containing anthracene and found it exhibits reversible fluorescence48.\nIn 2024, Hu et al. reported a multi-component eutectogel using a benzene ring as the\nluminescent unit49.”\nResults Section, Preparation and photophysical properties of eutectogels: It is worth\nmentioning that the RTP lifetime and QY of PAM-TD outperform the majority of previously\n90\nreported UOP materials based on NTLs (Supplementary Table 1).\nSupplementary Information:\nSupplementary Table: Supplementary Table 1 has been included.\nSupplementary Table 1. The phosphorescence performance of some UOP materials based on\nNTLs.\n Afterglows/ QYs (%) Ref.\n𝐞𝐦\n(nm)\nRTP lifetimes\nSA-Ca2+ 518 49.0 ms (τ ) 6.4 (Tot.) S1\nP\nD-Xyl crystals 435- 274-739 ms (τ ) 2.2 (Tot.) S2\nP\nCAA crystals 506 862 ms (τ ) 2.1 (Phos.) S4\nP\nHydantoin crystals 458- 1740 ms (τ ) 21.8 (Phos.) S5\nP\nP\noligomers 514\nAmmonium 460- 1630 ms (τ ) / S7\nP\npentaborate 540\nBSA 495 34.0 ms (τ ) 10.2 (Tot.) S8\nP\nCTAB crystals 490 761.9 ms (τ ) 14.7 (Tot.) S9\nP\nBVSM crystals 580 35.4 ms (τ ) / S10\nP\nPCDs 494 658.11 ms (τ ) 28.77 (Tot.) S11\nI-1 P\nTwo-dimensional 483 534.6 ms (τ ) / S12\nP\ncoordination polymer\nCE-PAAm gel 512 342 ms (τ ) 0.4 (Phos.) 41\nP\nPVA/BIU/PMAc 536 782 ms (τ ) 5.6 (Phos.) 37\nP\nPAA/DETA-Br 525 73.44 ms (τ ) 4.76 (Phos.) S13\nP\nPVA/PAM-NaIL 475 112.4 ms (τ ) / S14\nP\nAmorphous composite 524 1300 ms (τ ) 23.8 (Phos.) S15\nP\nof boroamide\nThis work 494 622.5 ms (τ ) 17.6 (Phos.)\nP\n9. There are some grammatical errors in the manuscript, authors should check them carefully.\nResponse: We have carefully checked and corrected the grammatical errors and the\nexpressions. The revised parts have been marked in the manuscript.\nReviewer #3\nI co-reviewed this manuscript with one of the reviewers who provided the listed reports. This\nis part of the Nature Communications initiative to facilitate training in peer review and to\nprovide appropriate recognition for Early Career Researchers who co-review manuscripts.\nResponse: Thank you very much for your kind comments and insightful suggestions.\nReviewer #4\nIn this manuscript entitled \"Nonaromatic Eutectogels with Ultralong Room-temperature and\nHigh-temperature Phosphorescence\", Zhong et al. report the fabrication of a novel type of pure\norganic phosphorescent materials through a simple solvent change treatment of a\npolyacrylamide (PAM) hydrogel with a non-aromatic bromine-containing deep eutectic solvent\n(DES) followed by wet annealing at an elevated temperature. The obtained eutectogels exhibit\nlong room-temperature phosphorescence of 622.5 ms and excellent high-temperature\nresistance. To my best knowledge, this is the first report of phosphorescent eutectogels whose\nphosphorescence emissions do not rely on traditional phosphors, signifying a new area in the\ndevelopment of novel DES containing materials. Moreover, the authors also provided a\nconvincing explanation of the photoluminescence mechanism through very detailed structural\ncharacterizations and theoretical calculations. I do believe that the significant novelty and\npotential applications of this work meet the high standards of Nature Communications.\nTherefore, the publication of this manuscript is strongly recommended. The authors need to\naddress the following issues to refine the manuscript.\nResponse: Many thanks for your kind comments on the feature of our work and your very\nconstructive and insightful suggestions.\n1. The Experimental part. Some experimental parameters, such as the delay time of the\nphosphorescence spectrum, the camera parameters for taking pictures, should be provided.\nResponse: We are very sorry for not being able to provide the complete experimental\nparameters.\nThe delay time for all delayed spectra was 1 ms. The camera parameters have been\nsupplemented in the experimental section.\nRevisions in the Manuscript:\nExperimental Section: The prompt and delayed spectra (delay time: 1 ms).... “Photographs\nand movies of the gel samples under and after the irradiation of lights were taken with Vivo\nX90 Pro cell phone (Vivo, China) using professional mode in a dark room and photographs of\ndelayed emissions were taken after turning off the light for 0.1 s. The ISO is set to 1/2000 and\nthe shutter speed is set to 1/15 s.” was supplemented.\n2. The author should explain the reason for choosing polyacrylamide (PAM) as the eutectogel\nmatrix rather than other polymers. And do the eutectogels involving other common polymers\nsuch as polyacrylic acid (PAA) also have outstanding phosphorescent properties?\nResponse:\nThe reasons for choosing PAM as the eutectogel matrix are as follows: 1) PAM is a kind of\npolymer without any aromatic structures, which provides a prerequisite for us to construct a\nnon-aromatic phosphorescent system. The PAM hydrogel used in this work was prepared by\nthermally initiated free-radical polymerization of AM (using KPS as the initiator) without using\nany chemical crosslinkers, avoiding the introduction of other aromatic luminescent molecules.\n2) PAM has been found to exhibit intrinsic fluorescence and RTP emissions in solid state and\nin some highly crosslinked hydrogels, since the clustering of amide groups enables efficient\nthrough-space conjugation (TSC) and the presence of abundant O and N atoms facilitates the\noccurrence of inter-system crossing (ISC) between singlet and triplet states. By studying the\ndifferences in the photoluminescence (PL) behaviors, structures as well as the interactions\nbetween the PAM eutectogels and the pure PAM xerogel, it is possible to understand how the\ndeep eutectic solvents (DESs) affect the PL behaviors especially the phosphorescence\nemissions of the eutectogels.\nWe agree with your comment that eutectogels involving some other common polymers may\nalso have outstanding phosphorescent properties.\nFollowing your suggestion, we have prepared polyacrylic acid (PAA) hydrogel, PAA-X xerogel\nand PAA-TD eutectogel using the same preparation methods as those for the PAM gels.\n90\nshown in Supplementary Fig. 27. The prompt and delayed max of PAA-X are 444 nm and\nem\n482 nm (Supplementary Fig. 27a, b), and those of PAA-TD are 490 nm and 542 nm,\n90\nrespectively (Supplementary Fig. 27d, e), suggesting that the DES solvent exchange and wet\nannealing are also very effective in red-shifting the emissions of PAA. For comparison, the\nprompt and delayed max of PAM-X are 369 nm and 458 nm, and those of PAM-TD are\nem 90\n404 nm and 494 nm, respectively. Obviously, PAA-X and PAA-TD exhibit significantly red-\n90\nshifted prompt and delayed emissions than corresponding PAM-X and PAM-TD , suggesting\n90\nthat using some other polymers like PAA can achieve more red-shifted prompt and delayed\nemissions than PAM.\nUnfortunately, PAA-TD only exhibits a short RTP lifetime of 32.3 ms ((Supplementary Fig.\n90\n27f), which is much shorter than that of PAA-X (415 ms) (Supplementary Fig. 27c). The\npossible reason is that the interactions between DES and PAA in PAA-TD are not as strong\n90\nas those in PAA-X.\nWe will continue exploring polymer systems suitable for this strategy and developing different\ntypes of eutectogels in the subsequent experiments.\n(a) (b) (c)104\ne n\nsit y 444 E E x m\ne n\nsit y 482 E E x m\n103\n415  P ms\nnt nt\nd\nP L I\nd\nP L I\no\nu nt s 102\ne e C\nz z\nm\nali\nm\nali\n101\nor or\nN N\n100\n300 400 500 600 700 300 400 500 600 700 0 100 200 300 400\nWavelength (nm) Wavelength (nm) Time (ms)\n(d\ne n\nsit y ) 490 E E x m (e\ne n\nsit y ) 542 E E x m (f)\n1\n1\n0\n0\n3\n4 32.3  P ms\nnt nt\nd\nP L I\nd\nP L I\no\nu nt s 102\ne e C\nm\nali z\nm\nali z\n101\nor or\nN N\n100\n300 400 500 600 700 300 400 500 600 700 0 100 200 300 400\nWavelength (nm) Wavelength (nm) Time (ms)\nSupplementary Fig. 27. Photophysical properties of the PAA-X xerogel and PAA-TD\n90\neutectogel. (a, b) Prompt (a) and delayed (delay time = 1 ms) (b) excitation and emission spectra\nof PAA-X under the corresponding max and max. (c) Phosphorescence lifetime decay\nem ex\nprofiles of PAA-X. (d, e) Prompt (d) and delayed (e) excitation and emission spectra of PAA-\nTD under the corresponding max and max . (e) Phosphorescence lifetime decay\n90 em ex\nprofiles of PAA-TD .\nManuscript:\nResults Section, Universality of the strategy: The following paragraph has been added.\nPhosphorescent eutectogels can also be prepared by using some other non-aromatic polymers.\nPolyacrylic acid (PAA) xerogel (PAA-X) and PAA-TD eutectogel were prepared by using\n90\nthe same preparation methods as those for the PAM gels, and their photophysical properties\nare shown in Supplementary Fig. 27. The prompt and delayed max of PAA-X are 444 nm\nem\nand 482 nm, and those of PAA-TD are 490 nm and 542 nm, respectively, suggesting that the\nof PAA. PAA-X and PAA-TD exhibit significantly red-shifted prompt and delayed emissions\n90\nthan corresponding PAM-X and PAM-TD , suggesting that using some other polymers like\nPAA-TD only exhibits a short RTP lifetime of 32.3 ms, which is much shorter than that of\nTD are not as strong as those in PAA-X.\nSupplementary Methods: Preparation of PAA, PAA-X and PAA-TD gels\n90\neutectogel are the same as those for the corresponding PAM gels. In brief, a PAA hydrogel\nwith a water content of 57 wt % was prepared with free-radical polymerization method, then it\nwas subjected to solvent exchange in an excess of TBAB-DBPA (TD) DES for 48 h to obtain\nan eutectogel PAM-TD , followed by annealing at 90C for 1.5 h, obtaining a PAM-TD\nRT 90\neutectogel. A PAA-X xerogel was obtained by complete drying of the PAA hydrogel in a\nnitrogen atmoshpere.\nSupplementary Figures: Supplementary Fig. 27 is added.\n3. It is not rigorous and reasonable for the authors to merely change different types of DES and\nconclude that ionic bromine may enhance phosphorescence performance. Theoretically,\ncovalent bromine can significantly enhance intersystem crossing, while the role of ionic\nbromine is different (Aggregate, 2021, 2, 13). It is suggested to modify the description in the\nmanuscript and further discuss which factor leads to the significant improvement of\nphosphorescence performance of eutectogels.\nResponse: Thank you for your professional advice.\nWe do accept it is improper to conclude that ionic bromine is more efficient in enhancing the\nphosphorescence performance of the gels. In this work, the eutectogels prepared with the DESs\ncontaining neutral bromo groups (CHCl-DBPA) or bromide ions (TBAB-BPA and PAM-\nTBAB-BMT) all exhibit larger max , longer phosphorescence lifetimes and the higher\nem\nphosphorescence QYs than the eutectogel prepared with the DES without any bromine atoms\n(CHCl-MU), suggesting that the heavy atom effect of bromine element contributes\nsignificantly to the excellent phosphorescence properties of the PAM eutectogels.\nRevisions in the Manuscript:\nResults Section, Universality of the strategy: Obviously, the eutectogels prepared with the\nDESs containing neutral bromo groups (CHCl-DBPA) or bromide ions (TBAB-BPA and PAM-\nTBAB-BMT) all exhibit larger max , longer phosphorescence lifetimes and the higher\nem\nphosphorescence QYs than the eutectogel prepared with the DES without any bromine atoms\n(CHCl-MU), suggesting that the heavy atom effect of bromine element contributes\nsignificantly to the excellent phosphorescence properties of the PAM eutectogels.\n4. Generally speaking, the introduction of heavy atoms, although it helps to promote\nphosphorescence in the system and increase the quantum yield, inevitably shortens the\nphosphorescence lifetime. But, in this work, the phosphorescence lifetime of the eutectogel is\nprolonged. The current manuscript is still somewhat vague in the explanation of the mechanism.\nIt is suggested that the authors separately describe the role of different steps in the strategy in\nsimultaneously achieving the improvement of phosphorescence lifetime and quantum yield.\nResponse: Thanks for the suggestion.\nRevisions in the Manuscript:\nResults Section, PL mechanism of eutectogels: The related texts in this section has been\nrevised as follows: the experimental and theoretical results confirm that wet annealing plays\ntwo key roles: 1) It redissolves PAM and establishes strong PAM-DES interactions, introducing\nheavy-atom DES into the phosphorescence system for strong SOC and high ISC efficiency,\npromoting phosphorescence generation and enhancing phosphorescence QYs. 2) Structural\nrearrangement forms a stable hydrogen bonding network and expands TSC, which increases\nsystem rigidity and suppresses nonradiative triplet exciton transitions, significantly prolonging\nthe phosphorescence lifetimes.\n5. The author explained that the interactions between DES and the polymer main chain affect\nthe phosphorescence properties of the system. It is well known that acrylamide is highly\nhydrophilic, and the DES used in this work contains tetrabutylammonium bromide, a highly\nhydrophobic component with large steric hindrance, which aggravates the aggregation of the\npolyacrylamide main chain during the solvent exchange process. If a DES containing heavy\natoms with better compatibility with the acrylamide unit is used, could more DES be introduced\nto enhance the phosphorescence performance of the system?\nResponse:\nFollowing your suggestion, we selected tetramethylammonium bromide (TMAB, with a\nsmaller steric hindrance and stronger hydrophilicity than TBAB) and DBPA with a molar ratio\nof 1:1 to form a new DES (TMAB-DBPA, named as TMD), and prepared PAM-TMD using\n90\nthe same methods described in this work.\n(a\nsit y\n)\n(b\nsit y\n)\n(c)104\n411  .8 P ms\ne n e n 103\nnt nt\nz e d P L I z e d P L I C o u nt s 102\nali ali\nm m 101\nor or\nN N\n100\n300 400 500 600 700 300 400 500 600 700 0 1 2 3 4\nWavelength (nm) Wavelength (nm) Time (s)\nSupplementary Fig. 26. Photophysical properties of the PAM-TMD eutectogel.\n90\n(a, b)\nPrompt (a) and delayed (delay time = 1 ms) (b) excitation and emission spectra under their\ncorresponding max and max. (c) Phosphorescence lifetime decay profile.\nem ex\nThe photoluminescence performance of the PAM-TMD eutectogel was measured. The\n90\nprompt and delayed max of PAM-TMD (Supplementary Fig. 26) are both red-shifted\nem 90\ncompared with those of PAM-TD (Fig. 2c, e), but the RTP lifetime of PAM-TMD (411.8\n90 90\nms) is shorter than that of PAM-TD (622.5 ms). These results may suggest that the use of a\nbeneficial to the formation of more extended TSC and hence red-shifted emission of the PAM-\nTMD eutectogel. However, on the other side, the lowered steric hindrance of the DES and\n90\nthe lowered incompatibility between the DES and the polymer may lead to the decreased\nrigidity of the gel system, and hence the decreased RTP lifetime.\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nResults Section, Universality of the strategy: It is necessary to mention that some other\nstructural factors of the DES should affect the interactions and compatibility between the\npolymer and DES and hence the PL behaviours of the eutectogels. For example, we selected\ntetramethylammonium bromide (TMAB, with a smaller steric hindrance and stronger\nhydrophilicity than TBAB) and DBPA with a molar ratio of 1:1 to form a DES (TMAB-DBPA,\nnamed as TMD), and prepared PAM-TMD using the same methods described in this work.\nem 90\ncompared with those of PAM-TD (Fig. 2c, e), but the RTP lifetime of PAM-TMD (411.8\n90 90\nms) is shorter than that of PAM-TD (622.5 ms).\nSupplementary Figures: Supplementary Fig. 26 is added.\n6. A similar strategy has been reported to enhance the mechanical properties of polyvinyl\nalcohol (PVA) eutectogels. The related references are better to be cited and elaborate on the\nsimilarities and differences of such strategies in polyacrylamide (PAM) gels.\nResponse:\nIn fact, we noticed the strategies for enhancing the mechanical properties of PVA gels,\nincluding solvent exchange with DESs and wet annealing and we have cited the relevant\nliterature [45] in the original manuscript. Here we included one more literature [46] in the\nrevised manuscript.\nRevisions in the Manuscript:\nIntroduction: Eutectogels, a novel type of materials utilizing deep eutectic solvents (DESs) as\nthe continuous phase, has recently emerged as promising alternatives to traditional hydrogels,\nowing to their structural tunability and exceptional thermal stability (-80 to 100C)43-46.\nReferences: 46 Du, S., Chen, X. D., Li, M. M., Peng, B. L., Lyu, Q. Q., Zhang, L. B. & Zhu,\nJ. T. Ultratough and highly conductive supramolecular poly(vinyl alcohol) eutectogels via a\nsequentially enhanced strategy. Adv. Funct. Mater., 35, 2409726 (2025).\nPoint-by-point Response to Reviews’ Comments\nWe sincerely thank the editor and all the reviewers for your careful reviewing of our\narticle and for offering insightful and valuable comments. We have once again carefully\nconsidered each of the editor's and reviewers' suggestions and made substantial\nrevisions to the manuscript accordingly.\nBelow, we provided point-by-point responses to all comments raised, with\ncorresponding changes highlighted in the revised manuscript and supplementary\ninformation. For clarity and ease of review, we have used the following formatting\nconventions in this response document: our responses to the reviewers' comments are\npresented in blue text, while all revisions made in the manuscript and supplementary\ninformation are highlighted in yellow. We hope this formatting will facilitate the review\nprocess and make it easier to track the changes we have made in response to the valuable\nfeedback.\nReviewer #1 (Remarks to the Author):\nI have carefully reviewed the revised manuscript and the response to the reviewers. The\nauthors have satisfactorily addressed all of my previous concerns. I therefore\nrecommend this work for publication in Nature Communications.\nResponse: Many thanks for your kind comments.\nReviewer #2 (Remarks to the Author):\nAs a reviewer, I find that this study has observed an interesting phenomenon, but its\ncurrent presentation resembles more of a \"technical report\" than a rigorous \"scientific\npaper.\" Furthermore, I believe the manuscript still suffers from fundamental\nshortcomings in scientific rigor and depth of mechanistic explanation, which prevent it\nfrom meeting the publication standards of this journal.\nResponse:\nWe sincerely appreciate you and your co-reviewer for providing very positive and\nconstructive comments and suggestions in the early round of reviewing. We have\nperformed the experiments suggested by you, provided point-by-point responses to all\ncomments, and made substantial revisions to the manuscript accordingly.\nThank you again for your time and efforts in re-reviewing our revised manuscript. We\nhave carefully considered your new comments, and have redesigned and performed\nmore experiments to provide a more in-depth mechanistic explanation of the high-\ntemperature phosphorescence (HTP) of the materials. The manuscript has been\nsignificantly revised accordingly.\nHowever, frankly speaking, we do not agree with some of the comments on the novelty\nof our work and the judgement of our manuscript a \"technical report\" rather than a\nrigorous \"scientific paper.\"\nFirst of all, we developed a novel type of materials with ultralong organic\nphosphorescence (UOP) and high-temperature phosphorescence (HTP) by solvent\nexchange of an NTLs-based hydrogel with a bromine-containing DES, followed by wet\nannealing. The PAM-TD gel exhibits outstanding RTP performance, with a long\n90\nlifetime of 622.5 ms, and especially a phosphorescence QY of 17.6%, which is the\nhighest reported for non-traditional luminescent gel systems and even polymer systems\nin solid state. More importantly, this is the first report of NTLs possessing HTP.\nTherefore, this work represents a significant advantage or breakthrough in the\ndevelopment of non-traditional luminescent materials.\nMoreover, except for the measurements of the photoluminescence and mechanical\nproperties of the materials, we have also carefully characterized the microstructures and\nthe interactions in them with several techniques (e.g., DMA, DSC, SEM, WXRD,\nSAXS, LF-NMR, FT-IR). In addition, we have conducted a series of control\nexperiments by comparing the relationship between the photophysical properties and\nstructures of the PAM hydrogel without DES (PAM-H), PAM xerogels (PAM-X), PAM-\nTD prepared with only solvent exchange but without annealing, complexes with only\nRT\none component of the DES (TD), and various DES-containing complexes with or\nwithout heavy atoms. Finally, we carried out theoretical calculations to further\nunderstand the formation of strong interactions between PAM and DES and the\noccurrence of phosphorescence.\nThese experimental and theoretical results all confirm the transformation of\nmicrostructures and the formation of strong hydrogen bonding during the solvent\nexchange and wet annealing processes. This is the main reason for the dramatically\nenhanced and redshifted PL emissions of the PAM-TD complexes.\nWe do believe that we have provided a detailed and thorough explanation for the RTP\nperformance of the gels in this work. Therefore, this manuscript is not a \"technical\nreport\".\nIn the revised version of this manuscript, following your comment, we performed TGA,\nin-situ variable-temperature SAXS and in-situ variable-temperature FTIR experiments\nto further confirm the structure stability of PAM-TD at high temperatures and provide\n90\nan explanation of the HTP performance of the complexes.\nHope you can find that our responses to your comments are reasonable and the revisions\nmade to the manuscript and supporting information are acceptable.\nThe decision is primarily based on the following reasons:\nWhile you have provided supplementary FTIR data in response to the request for key\nevidence regarding solvent exchange time, this only constitutes a \"post hoc\nverification\" of a preselected parameter, rather than a systematic \"process exploration.\"\nResponse: Thanks for this comment.\nWe do not agree with the comment that “this only constitutes a ‘post hoc verification’\nof a preselected parameter, rather than a systematic ‘process exploration’.”\nThe 48-hour solvent exchange time is not a preselected parameter. It is based on the\nfact that the gel weight remains constant after 24 h solvent exchange. A longer solvent\nexchange time (48 h) was selected to ensure the completion of solvent exchange and\nthe formation of a stable structure.\nFollowing your previous comments, in the revised manuscript and SI, we provided\nFTIR spectra of PAM-TD gel samples prepared with different DES solvent exchange\ntime (Supplementary Fig. 1a), which showed the dynamic evolution of the hydrogen\nbonding interactions during the solvent exchange process and also proved the rationale\nof the 48-hour solvent exchange time. This should be a systematic “process\nexploration”.\nThe selection of other experimental parameters (e.g., the components and contents of\nthe gels, reaction time, annealing temperature and time, etc.) were also selected to\noptimize the RTP and HTP performances of the gels.\nThe explanation of key physicochemical mechanisms remains superficial and lacks\ndepth. Although terms like \"hydrogen bond rigidification\" and \"heavy-atom effect\" are\nfrequently mentioned, the revised manuscript still does not provide deeper insights.\nThis is particularly evident in the insufficient exploration of the mechanism behind the\ninnovative achievement of high-temperature phosphorescence (HTP).\nResponse: Thanks for this comment.\nWe accept the comment “insufficient exploration of the mechanism behind the\ninnovative achievement of high-temperature phosphorescence (HTP)”.\nWe reviewed the reports on high-performance HTP materials published recently,\nfocusing on their explanations on HTP mechanisms and the experimental and\ntheoretical methods they used.\nHuang and co-workers constructed organic doped HTP materials by using planar rigid\nmolecules as guests and polymers with high glass transition temperatures as hosts (Nat.\nComm., 2024, 15, 1269). Through theoretical calculations, they obtained the torsion\nangles and thermodynamic parameters of two guests at various temperatures, and\nconcluded that planar rigid structure of the guests resisted molecular thermal motion at\nhigh temperatures, thereby reducing non-radiative transitions. By using polymers with\ndifferent glass transition temperatures as hosts, they concluded that the rigid\nenvironment provided by the host matrix further restricted the molecular motion of the\nguest. And finally, they concluded that the guest-host twofold rigidity activated the HTP\nproperties of the doped materials.\nMa and co-workers achieve daylight-excited efficient phosphorescence and tunable\nafterglow at high temperature in flexible polymer films through host-guest hydrogen-\nbonding (Nat. Comm., 2025, 16, 9668). Through control experiments and DFT\ncalculations, they concluded that the excited-state conformation of phosphors\nundergoes a temperature-dependent transformation, which drives the observed\nphenomena.\nZhang and co-workers reported a dye-doped, cross-linked epoxy resin with sensitive\nmechanical compression-patterned phosphorescence. The doped polymers showed both\nfull-color room-temperature phosphorescence and high-temperature phosphorescence\nwith ultralong lifetimes (Nat. Comm., 2025, 16, 10163). They found that the\ntemperature range over which phosphorescence occurs can be modulated by the T\ng\nvalues of the epoxy resins.\nChen and co-workers adopted an efficient multivalent assembly strategy to prepare a\n\"rose\" structured supramolecular assembly, which firmly fixed the organic phosphor\nand thus achieved high-temperature liquid-phase phosphorescence (HTLP) (Angew.\nChem. Int. Ed., 2025, e202423650). The employed TGA and several variable-\ntemperature experiments (FTIR, Raman, XRD, and SEM) to confirm that the structures\nand interactions in the \"rose\" supramolecular structure remain intact at high\ntemperatures. They also used multifunctional phosphors with more binding sites to\nenhance multivalent interactions, further verifying the effectiveness of this strategy.\nFinally, they concluded that the multivalent assembly strategy can effectively achieve\nhigh-temperature long afterglow materials.\nYang and co-workers constructed HTP composite materials by doping phosphors into\nhydrophobic and highly rigid cycloolefin copolymers (COC) (Adv. Mater., 2025,\n2416397). Through in situ variable-temperature FTIR spectra studies on the changes in\nhydrogen bonds between the host and guest during heating, they concluded that the\ncyclic skeleton and the bulky adamantanyl side groups are in favor of protecting the\nhydrogen bonding and electrostatic interactions from dissociation and suppressing the\nnon-radiative decay of triplet exciton, even under elevated temperature. They also\ninvestigated the influence of phosphors with different rigidities on HTP and concluded\nthat the rigidity of the phosphor would also affect the HTP performance of the system.\nFinally, they concluded that the high rigidity of the COC matrix and the rigid phosphor\njointly promote the HTP performance of the system.\nFrom these studies, we can find that the explanation of the mechanism of RTP and\neven HTP mainly relies on the rigid structures of the systems and their stability at\nhigh temperatures.\nIn our work, we have measured the T of PAM-TD , PAM-TD and PAM-TD\ng RT 60 90\neutectogels with DMA and DSC. The significantly higher T of PAM-TD suggests its\ng 90\nhigh rigidity. Through SEM and SAXS measurements, we verified that the annealed\nPAM-TD has a more compact structure, smaller average chain spacing, and less phase\n90\nseparation than the unannealed PAM-TD Through FTIR and LF-NMR, we confirmed\nRT.\nthat strong hydrogen bonds are formed inside PAM-TD . We also verified through\n90\ntheoretical calculations that strong interactions are formed between PAM and DES after\nannealing, and ISC was highly likely to occur to generate triplet states. In addition, we\nalso added various DESs containing (or not containing) heavy atoms as control\nexperiments to further verify the source of phosphorescence.\nIn summary, the strong hydrogen bonding interactions between PAM and DES leads to\nthe rigidified molecular conformations, which largely promote the excellent\nphosphorescence performance of PAM-TD at room temperature and even at high\n90\ntemperatures.\nFollowing your comment, we performed thermogravimetric analysis (TGA), in-situ\nvariable-temperature SAXS and FTIR experiments and theoretical calculations to\nfurther confirm the structure stability of PAM-TD .\nexperimental and theoretical results are included and discussed.\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nResults: RTP and HTP mechanisms\nThe above experimental and theoretical results all confirm the transformation of\nmicrostructures and the formation of strong hydrogen bonding during the solvent\nexchange and wet annealing processes. This is the main reason for the dramatically\nenhanced and redshifted PL emissions of the PAM-TD complexes. For the PAM\nxerogels, drying process leads to the removal of water, and hence the close contact of\namide groups and the formation of hydrogen bonds among PAM chains. For the PAM-\nTD complexes, the solvent exchange and wet annealing treatments also lead to the\nremoval of water, and hence the close contact of amide groups and the formation of\nstrong hydrogen bonding among PAM chains and between PAM and DES. Both PAM\nxerogels and PAM-TD complexes exhibit dramatically enhanced fluorescence\nemissions than the PAM hydrogel. The reason is that the hydrogen bonding is effective\nin rigidifying the molecule conformations and hence inhibiting non-radiative transitions.\nThe PAM xerogels and PAM-TD complexes also exhibit redshifted fluorescence\nemissions than the PAM hydrogel. The reason is that that the close contact of amide\ngroups, which are typical NCCs, leads to the formation extended TSC and hence\nreduced energy gaps between ground and excited states. The PAM-TD complexes\nexhibit more redshifted fluorescence emissions than the corresponding PAM xerogels.\nThe reason is the formation of more and stronger hydrogen bonding between DES and\nPAM and hence the formation of more extended TSC.\nThe experimental results prove that the introduction of DES into the PAM gel through\nsolvent exchange and wet annealing at an elevated temperature is essential to the RTP\nemissions of the complexes. To further understand the origin of phosphorescence\nemission, spin-orbit coupling (SOC) constants (ξ) of the PAM-DES complexes and\nPAM xerogels were calculated. In the PAM-TD complex, using three repeating units of\nPAM, one TBAB molecule and one DBPA molecule as the model (Fig. 4b), the energy\ngaps between S and T , T , and T are very small (< 0.3 eV), easily facilitating ISC.\n1 1 2 3\nVery impressively, ξ(S , T ), ξ(S , T ), ξ(S , T ), and ξ(S , T ) are very large, with ξ(S ,\n0 1 1 1 1 2 1 3 1\nT ) reaching 1005.91 cm-1, confirming that PAM-TD undergoes efficient ISC to\n2\ngenerate triplet excitons. On the contrary, the PAM xerogel exhibits low ξ (Fig. 4d). In\naddition, natural transition orbital (NTO) simulations show that the highest occupied\nnatural transition orbital (HONTO) is concentrated on the bromide anions of TBAB,\npart of PAM, and interaction zones, while the lowest unoccupied natural transition\norbital (LUNTO) is mainly distributed on DBPA, verifying electron transfer between\nPAM and DES (Fig. 4c). These theoretical calculation results well explained the easier\noccurrence of RTP of the PAM-DES complexes than the PAM gels.\nFig. 4: Theoretical calculations of RTP mechanism of complexes. (a) The visualization\nof IRI isosurfaces of PAM-TD (top-left), PAM-X (top-right) and the standard\n90 90\ncoloring method and chemical explanation of sign(λ )ρ (bottom). (b, d) Energy level\n2\ndiagrams and SOC constants of PAM-TD (b) and PAM-X (d), calculated with time-\n90 90\ndependent density functional theory (TD-DFT). (c) Simplified and simulated natural\ntransition orbits of PAM-TD (left) and PAM-X (right). The model includes three\n90 90\nrepeating units of PAM, one TBAB molecule and one DBPA molecule.\nThe PAM-TD complexes, especially those prepared at elevated temperatures, exhibit\nredshifted PL emissions, higher QYs, and longer phosphorescence lifetimes than the\ncorresponding PAM xerogels, suggesting that wet annealing plays important roles in\nthe RTP emission of the PAM-TD complexes. Wet annealing leads to the redissolution\nof PAM and establishes strong PAM-DES interactions, leading to the high SOC and\nISC efficiency, therefore promoting phosphorescence generation and enhancing\nphosphorescence QYs. On the other hand, the formation of strong hydrogen bonding\nbetween PAM and DES leads to more extended TSC and rigidified molecular\nconformations, and hence the redshifted and significantly prolonged RTP emissions.\nHTP performances of organic materials based on TLs are generally explained with the\nrigid structures of the systems and their stability at high temperatures25,27,28,55,56. The\nsignificantly higher T of PAM-TD than other complexes and xerogels suggests its\ng 90\nhigh rigidity, and this is the reason for its excellent HTP. Here we performed\nthermogravimetric analysis (TGA), in-situ variable-temperature SAXS and FTIR\nexperiments and theoretical calculations to further confirm the structure stability of\nPAM-TD .\nbelow 150°C (Supplementary Fig. 24). The more significant mass loss in the 150-250°C\ntemperature range of PAM-TD than PAM-TD can be attributed to the evaporation\nRT 90\nof free DES that is not hydrogen bonded with PAM. Upon heating up to 150C, the 2D\nSAXS patterns of PAM-TD show almost equally sized dispersion rings (Fig. 5a). The\n90\n1D profiles almost completely coincide as the temperature increases, with only slight\ndecrease in the scattering intensity in the low q region (< 0.3 nm-1), and very slight\nincrease in the high q region (> 0.3 nm-1) (Fig. 5b, and Supplementary Fig. 25a).\nThe\nPorod plots derived from the 1D SAXS profiles are nearly smooth in the high q region\n(Supplementary Fig. 25b), and the calculated correlation length (ξ) only slightly\nincreases from 11.8 Å at 40°C to about 12.9 Å at 150°C (Fig. 5c). In addition, the\naverage radius of gyration (R ) of the polymer chain in the low q region, calculated\ng\nfrom the Guinier plot (Supplementary Fig. 25c), decreases by 2.03 nm when heated\nfrom 40°C to 150°C (Fig. 5d). These results confirm that the structure of PAM-TD\n90\nremains compact during the heating process, with only very slight structural loosening.\nFig. 5. Characterization of temperature tolerance of PAM-TD at different\n90\ntemperatures. (a). In-situ variable-temperature 2D SAXS patterns of PAM-TD . (b)\n90\ncorrelation length (ξ) (c) and histograms of the radius of gyration (R ) (d) derived from\ng\nthe 1D profiles. (e-f) In-situ variable-temperature ATR-FTIR spectra of PAM-TD ,\n90\nand\nthe enlarged absorption bands of amino groups in e (f). (g-h) In-situ variable-\ntemperature ATR-FTIR spectra of PAM-TD , and the enlarged absorption bands of\nRT\namino groups in g (h). (i) The percentage of transmittance of the amino peaks of PAM-\nTD and PAM-TD relative to that at 30°C during heating process. (j) The\nRT 90\nwavenumbers of the amino peaks of PAM-TD and PAM-TD with various\nRT 90\ntemperatures. (k-m) Optimized DES (TD), PAM-PAM, and PAM-TD cluster models\nwere used to simulate the temperature-dependent change in Gibbs free energy via\nShermo. (n). Gibbs free energy decrease (%) for DES (TD), PAM-PAM, and PAM-TD\ncluster upon heating from 20°C to 150°C. (o) Schematic illustration about the thermo-\nassociated phosphorescence of PAM-TD (left) and PAM-TD (right).\nRT 90\nThe in-situ variable-temperature ATR-FTIR spectra of PAM-TD and PAM-TD were\nRT 90\nobtained (Fig. 5e, g). In the temperature range of 30°C to 150°C, the absorption bands\nattributed to the alkyl and carbonyl groups of PAM remains nearly no change, consistent\nwith the results of SAXS, confirming the long-range structural stability of the PAM-\nDES complexes at high temperatures. However, obvious differences are observed in the\nintensity and wavenumber of the amino absorption band of PAM-TD and PAM-TD\nRT 90\n(Fig. 5f, h). For PAM-TD , the intensity of amino group decreases slightly with\nRT\ntemperature till 60°C and then drops significantly, and the absorption wavenumber\nblueshifts from 3329 cm⁻¹ (30°C) to 3339 cm⁻¹ (60°C), but it gradually redshifts to 3315\ncm-1 at 90°C and 3304 cm-1 at 150°C. For PAM-TD , the intensity and wavenumber of\n90\nthe amino absorption band change very slightly with increasing temperature till 120°C\n(Fig. 5i, j), confirming that the chemical structure and hydrogen bonding in PAM-TD\n90\nare very stable below 120°C, and this is the reason for the phenomenon that PAM-TD\n90\nstill has a RTP lifetime of 366.2 ms at 120°C. A more significant change in the intensity\nand wavenumber of the amino absorption band of PAM-TD is observed when the\n90\ntemperature reaches 150°C, suggesting the breakage of hydrogen bonding interactions\nin it. This is the reason for the disappearance of phosphorescence emission at 145°C.\nNote that the wavenumbers of the absorption band of amino groups in PAM-TD\nRT\nabove 90°C are very close to those of PAM-TD , verifying the feasibility of using 90°C\n90\nto anneal PAM-TD .\nRT\nShermo calculations were used to simulate the thermodynamic parameter changes of\nDES (TD), PAM-PAM and PAM-TD clusters during the heating process. The internal\nenergy (U) and enthalpy (H) of the three systems all decrease gradually with increasing\ntemperature (Supplementary Fig. 26). Their Gibbs free energy (G) also decreases with\nincreasing temperature (Fig. 5k-m). The decreased percentage of G of PAM-TD is only\nabout 12.79% when the temperature rises from 20°C to 150°C, lower than those of\nPAM-PAM and especially DES (TD) (Fig. 5n). This again indicates the interactions\nbetween PAM and DES are very stable and not strongly affected by temperature.\nMethods: The related methods of characterization and theoretical calculation are\nprovided.\nSupplementary Information:\nSupplementary Figures: Supplementary Fig. 24-26 and the related texts are provided.\nSupplementary Fig. 24. Thermogravimetric analysis (TGA) curves of DES (TD),\nPAM-X, PAM-TD , and PAM-TD .\nRT 90\n)%(\nthgieW\n1 0\n8\n6\n4\n2\n0\n0\n0\n0\n0\nP\nP\nP\n1 0\nEAA\nA\nM\n(T\n-X-T\n-T\nD\nD\nD\n)\nR T\n9 0\n2 0 0\nT ( ° C\n3 0\n)\n0 4 0 0 5 0 0\nSupplementary Fig. 25. (a) In situ variable-temperature SAXS scattering intensities of\nPAM-TD at q = 0.1 nm-1 and q = 1 nm-1. (b-c) The corresponding Porod plot (b), and\nSupplementary Fig. 26. The changes of internal energy (U) and enthalpy (H) of the\nDES (TD) (a, d), PAM-PAM (b, e) and PAM-TD (c, f) models with temperature.\nThe novelty of this work is insufficient in the following two aspects:\nFirst, its performance improvement is limited compared to existing studies. The best-\nperforming sample in this work has undergone extensive drying and annealing. In\ncontrast, the PAM-TD hydrogel—which only underwent solvent exchange without\nRT\nannealing—exhibits a persistent luminescence lifetime of merely 208.1 ms. This\nperformance does not represent a significant advantage or breakthrough compared to\nmany previously reported non-traditional luminescent gel systems.\nResponse: Thanks for this comment.\nNote that there is no extensive drying during the gel preparation process and the PAM-\nTD gel is not a “hydrogel”.\nRT\nThe PAM-TD gel is an eutectogel prepared directly by solvent exchange of a PAM\nRT\nhydrogel with a DES, and the transformation of PAM-TD to PAM-TD by wet\nRT 90\nannealing is not a drying process, since it is carried out in a DES and the liquid in the\ngels is mainly the DES rather than water. Annealing at an elevated temperature leads to\nthe formation of more and stronger hydrogen bonds between PAM and DES, and hence\na denser network in the gels. This is the reason for the slightly lowered liquid contents\nof the annealed gels.\nThe PAM-TD gel exhibits a RTP lifetime of 208.1 ms. It is true that this performance\nRT\ndoes not represent a significant advantage or breakthrough compared to many\npreviously reported non-traditional luminescent gel systems.\nHowever, the PAM-TD gel is only an intermediate product. After annealing treatment,\nRT\nthe final product PAM-TD gel exhibits outstanding RTP performance, with a long\n90\nlifetime of 622.5 ms, and especially a phosphorescence QY of 17.6%, which is the\nhighest reported for non-traditional luminescent gel systems and even polymer systems\nin solid state (Supplementary Fig. 5).\nMore importantly, this is the first report of NTLs possessing HTP.\nTherefore, this work represents a significant advantage or breakthrough in the\ndevelopment of non-traditional luminescent materials.\n)%(\nsYQ\n.sohP\n2\n1\n1\n0\n5\n0\n5\n0\nS\nP\nP\nC\nP\nP\nC\nT\nw o -d im e n\n2+ A -C a\n-X Y\n-N D\nE -P A A M\nV A /B IU /P\nA A /D E T A\nM C S\nh is W o rk\n2 0 0\nR T P\ns io n a\nM A c\n-B r\nL i\nl c o\n4\nf e\no\n0\nt\nrd\n0\ni m\nin a tio\ne\nn p o\n6\n( m\nly\n0\n0\ns\ne r\n)\n8 0 0\nSupplementary Fig. 5. Comparison of RTP lifetimes, and phosphorescence QYs\nbetween PAM-TD and previously reported non-aromatic RTP polymer systems.\nManuscript:\nResults: It is worth mentioning that the phosphorescence performance of PAM-TD ,\n90\nwhich simultaneously features a long RTP lifetime and a high QY, outperforms most\npreviously reported NTL-based UOP material systems (Supplementary Table 1). This\nis particularly remarkable in the context of polymer NTLs, and its phosphorescence QY\nis the largest ever reported (Supplementary Fig. 5).\nSupplementary Information:\nSupplementary Figures: Supplementary Fig. 5 and the related texts are provided.\nSecond, the high-performance state deviates from the claimed material category. The\noutstanding phosphorescence performance reported in this work mainly originates from\nsamples after wet-annealing, at which point the system has extremely low water content\nand essentially exists in a quasi-solid state rather than a typical gel state. Equating the\nperformance of this highly dehydrated, rigid quasi-solid material with a breakthrough\nin \"eutectogels\" is conceptually misleading and blurs the true innovative scope of this\nwork.\nResponse:\nWe accept that the materials in this work exist in a quasi-solid state rather than a typical\ngel state. Materials made from DES and polymer through solvent exchange of a\nhydrogel with a DES are usually termed eutectogels. The only difference between the\nmaterials made in this work and other eutectogels is the low DES content (about 10\nwt%) in this work, due to the formation of very strong hydrogen bonding between the\nDES and PAM.\nFrankly speaking, we hesitated to the call the materials in this work eutectogels, but we\ncould not find a more suitable term then. Following your comment, to avoid misleading,\nwe choose to term the materials in this work as “polymer-DES complexes”.\nRevisions in the Manuscript and Supplementary Information:\nManuscript:\nIntroduction:\nBy solvent exchange with a bromine-containing DES followed by wet annealing on the\nPAM hydrogel, eutectogels were obtained. Due to the formation of very strong\nhydrogen bonding between PAM and the DESs, the DES contents in the eutectogels are\nonly about 10 wt%, lower than those of common eutectogels. Therefore, they are termed\nas “polymer-DES complexes” to distinguish them from common eutectogels.\nIn conclusion, the study identifies an interesting composite material with notable HTP\nproperties. However, due to the non-systematic optimization, the reliance on an\ninsufficient theoretical model, the lack of profound mechanistic insight—particularly\nfor HTP—and the conflation of solid-state and gel-state properties, the manuscript does\nnot provide the scientific depth or rigorous foundation required for publication in this\njournal.\nI encourage the authors to undertake a more fundamental investigation addressing these\npoints, which would likely require a significant redesign of the study.\nResponse:\nFollowing your comments and suggestions, we redesigned experiments and provide\nmore in-depth explanations to the RTP and HTP performances of the novel polymer-\nDES complexes in this work. We have made a major revision to the manuscript. Hope\nyou can find that our responses to your comments are reasonable and the revisions made\nto the manuscript and Supporting Information are acceptable.\nReviewer #3 (Remarks to the Author):\nI co-reviewed this manuscript with one of the reviewers who provided the listed reports.\nThis is part of the Nature Communications initiative to facilitate training in peer review\nand to provide appropriate recognition for Early Career Researchers who co-review\nmanuscripts.\nResponse: Many thanks for your comments.\nReviewer #4 (Remarks to the Author):\nBased on the previous comments, the author has made good revisions to the manuscript,\nand it is now accepted for publication.\nResponse: Many thanks for your comments.\nPoint-by-point Response to Reviews’ Comments\nReviewer #2 (Remarks to the Author):\nFollowing the previous suggestions, the author has made thorough revisions, and the\nmanuscript is now suitable for publication.\nResponse:\nThanks for your recognition of our manuscript."}, {"round": 2, "reviewer_comments": {"reviewer_1": "I have carefully reviewed the revised manuscript and the response to the reviewers. The authors have satisfactorily addressed all of my previous concerns. I therefore recommend this work for publication in Nature Communications.", "reviewer_2": "As a reviewer, I find that this study has observed an interesting phenomenon, but its current presentation resembles more of a \"technical report\" than a rigorous \"scientific paper.\" Furthermore, I believe the manuscript still suffers from fundamental shortcomings in scientific rigor and depth of mechanistic explanation, which prevent it from meeting the publication standards of this journal.\n\nThe decision is primarily based on the following reasons:\nWhile you have provided supplementary FTIR data in response to the request for key evidence regarding solvent exchange time, this only constitutes a \"post hoc verification\" of a preselected parameter, rather than a systematic \"process exploration.\"\nThe explanation of key physicochemical mechanisms remains superficial and lacks depth. Although terms like \"hydrogen bond rigidification\" and \"heavy-atom effect\" are frequently mentioned, the revised manuscript still does not provide deeper insights. This is particularly evident in the insufficient exploration of the mechanism behind the innovative achievement of high-temperature phosphorescence (HTP).\n\nThe novelty of this work is insufficient in the following two aspects:\nFirst, its performance improvement is limited compared to existing studies. The best-performing sample in this work has undergone extensive drying and annealing. In contrast, the PAM-TDRT hydrogel—which only underwent solvent exchange without annealing—exhibits a persistent luminescence lifetime of merely 208.1 ms. This performance does not represent a significant advantage or breakthrough compared to many previously reported non-traditional luminescent gel systems.\nSecond, the high-performance state deviates from the claimed material category. The outstanding phosphorescence performance reported in this work mainly originates from samples after wet-annealing, at which point the system has extremely low water content and essentially exists in a quasi-solid state rather than a typical gel state. Equating the performance of this highly dehydrated, rigid quasi-solid material with a breakthrough in \"eutectogels\" is conceptually misleading and blurs the true innovative scope of this work.\n\nIn conclusion, the study identifies an interesting composite material with notable HTP properties. However, due to the non-systematic optimization, the reliance on an insufficient theoretical model, the lack of profound mechanistic insight—particularly for HTP—and the conflation of solid-state and gel-state properties, the manuscript does not provide the scientific depth or rigorous foundation required for publication in this journal.\n\nI encourage the authors to undertake a more fundamental investigation addressing these points, which would likely require a significant redesign of the study.", "reviewer_3": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts.", "reviewer_4": "Based on the previous comments, the author has made good revisions to the manuscript, and it is now accepted for publication."}, "author_response": "Point-by-point Response to Reviews’ Comments\nWe sincerely thank the editor and all the reviewers for your careful reviewing of our\narticle and for offering insightful and valuable comments. We have once again carefully\nconsidered each of the editor's and reviewers' suggestions and made substantial\nrevisions to the manuscript accordingly.\nBelow, we provided point-by-point responses to all comments raised, with\ncorresponding changes highlighted in the revised manuscript and supplementary\ninformation. For clarity and ease of review, we have used the following formatting\nconventions in this response document: our responses to the reviewers' comments are\npresented in blue text, while all revisions made in the manuscript and supplementary\ninformation are highlighted in yellow. We hope this formatting will facilitate the review\nprocess and make it easier to track the changes we have made in response to the valuable\nfeedback."}, {"round": 3, "reviewer_comments": {"reviewer_2": "Following the previous suggestions, the author has made thorough revisions, and the manuscript is now suitable for publication."}, "author_response": "Response:\nThanks for your recognition of our manuscript."}]

Decision letter