# Sugar acids - the secret ingredient transforming hydrogels into elastic and stretchable materials

Rafal Bielas, Marine Tassé, Juliette Fitremann, Baptiste Martin, V. Collière, Gabor Molnar, Lionel Salmon, Azzedine Bousseksou

► To cite this version:

Rafal Bielas, Marine Tassé, Juliette Fitremann, Baptiste Martin, V. Collière, et al., Sugar acids - the secret ingredient transforming hydrogels into elastic and stretchable materials. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2025, 726, pp.138126. 10.1016/j.colSURFA.2025.138126. hal-05225329

HAL Id: hal-05225329

https://hal.science/hal-05225329v1

Submitted on 27 Aug 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

# Sugar acids - the secret ingredient transforming hydrogels into elastic and stretchable materials

Rafał Bielas<sup>a,c,*</sup> <sup>●</sup>, Marine Tassé<sup>a</sup>, Juliette Fitremann<sup>b●</sup>, Baptiste Martin<sup>a●</sup>, Vincent Collière<sup>a</sup>, Gabor Molnar<sup>a</sup>, Lionel Salmon<sup>a</sup>, Azzedine Bousseksou<sup>a</sup>

## GRAPHICAL ABSTRACT

<figure><img src="image_3.png" /></figure>

## ARTICLE INFO

**Keywords:**

Hydrogels

Sugar acid

Microphase separation

Lactobionic acid

## ABSTRACT

Presented study explores the modification of charged monomers through anion exchange to introduce sugar structures into polymers, enhancing their biological and physicochemical properties. The commercially available monomer 2-trimethylammonioethyl methacrylate chloride (TMAEMA/Cl) was subjected to a two-stage anion exchange, replacing chloride with lactobionate to yield TMAEMA/Lac. The resulting monomer was copolymerized via UV-initiated free-radical polymerization with hydroxyethyl acrylate (HEA), using N,N'-methylenebisacrylamide as a crosslinker and water as a solvent due to solubility constraints. Swelling tests revealed that TMAEMA/Cl hydrogels exhibited significantly higher swelling ratios (up to 1180 %) compared to TMAEMA/Lac (max 768 %). Opacity in TMAEMA/Lac samples suggested microphase separation, supported by AFM and Raman spectroscopy, which identified hydrophobic (polymer backbone-rich) and hydrophilic (lactobionate-rich) domains. Rheological analysis demonstrated enhanced elasticity in TMAEMA/Lac hydrogels sustaining deformations up to 1000 %. Thermal analysis revealed increased stability in lactobionate-based xerogels, with delayed decomposition (400–450°C) compared to TMAEMA/Cl. DSC indicated reduced glass transition temperatures ($T_g$) in lactobionate hydrogels, suggesting sugar-induced plasticization. Denser, less porous morphologies in TMAEMA/Lac hydrogels, correlating with lower swelling, were confirmed by means of SEM. These findings highlight the role of lactobionate in inducing polymerization-induced microphase separation (PIMS),

<footnote><sup>a</sup> Laboratoire de Chimie de Coordination, CNRS & University of Toulouse, 205 route de Narbonne, 31077 Toulouse, FRANCE</footnote>

<footnote><sup>b</sup> Softmat, Université de Toulouse, CNRS UMR 5623, Université de Toulouse III - Paul Sabatier, 118 route de Narbonne, Cedex 9, Toulouse 31062, FRANCE</footnote>

<footnote><sup>c</sup> Department of Pharmacognosy and Phytochemistry, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia in Katowice, Jagiellońska 4, Sosnowiec 41-200, POLAND</footnote>

<footnote>* Corresponding author at: Laboratoire de Chimie de Coordination, CNRS & University of Toulouse, 205 route de Narbonne, 31077 Toulouse, FRANCE. E-mail address: rafal.bielas@lcc-tonouse.fr (R. Bielas).</footnote>
altering mechanical, thermal, and morphological properties. The study provides a facile method to tailor
hydrogel properties through sugar-based anion exchange, with potential applications in biomaterials and soft
materials engineering.

# 1. Introduction

Hydrogels are materials most often based on polymer networks, containing large amounts of water [1,2]. The polymers used can be both of natural [3] and synthetic origin, and also depending on the needs and design, they can be chemically crosslinked [4] or not [5]. Due to their unique properties, such as biocompatibility [6,7] and even tissue-like behaviour [8], these materials have found wide use, especially in medicine-related disciplines [9], such as drug delivery [10,11], tissue engineering [12] or biosensors. Because of the fact that these materials can be swelled while maintaining mechanical properties, they are ideal for replacing and mimicking biological tissues [13,14].

The properties of the hydrogel can be modified and adapted to the needs by influencing the polymer structure [15], its modification by introducing specific functional groups [16], changing the degree of crosslinking [15,17] or modification of the external environment, such as pH [18], temperature [19,20] or ionic strength [21]. One of the less studied factors that can affect the hydrogel properties is the occurrence of microphase separation. It involves clearly separating phases showing different properties [22]. In the case of hydrogels, we usually deal with the separation of the hydrophilic and hydrophobic phases [23]. This phenomenon can be caused by manipulation of, e.g. temperature after the hydrogel creation, or in more interesting cases, may occur as a result of polymerization of previously well-mixed monomers.

Polymerization induced microphase separation (PIMS) leads to the formation of heterogeneous zones with different properties, which affects the performance of the entire hydrogel [24,25]. The mechanism, according to which PIMS occurs, is based on the impact between complex kinetic and thermodynamic factors. During polymerization, phase separation of polymer chains occurs due to the lack of miscibility between individual parts of the polymer or monomers [26]. The growing polymer network usually stops this separation at some stage, what leads to the creation of microdomains dispersed inside the hydrogel. Further, phase-separated microstructure can be modified through various factors, among which the degree of polymerization, temperature, the presence of solvents or the molar mass of individual components of the polymer network can be mentioned. What is more, control over phase separation via PIMS offers the possibility of designing micro- and nanostructure [27], and thus adapt the obtained hydrogels to advanced and demanding applications, such as drug delivery, tissue engineering [28,29] or self-healing materials [30–32].

Over the past twenty years, many studies have been conducted [33] that have allowed a better understanding of the PIMS process taking place in hydrogels and has opened new avenues to design highly organized or disorganized materials. For example, the incorporation of self-assembled block copolymers during the polymerization process can lead to the formation of microdomains with distinct functionalities, such as hydrophilic and hydrophobic regions or regions that respond to different environmental stimuli [34,35]. Such control over the microstructure of hydrogels offers new ways to design materials with enhanced or tuneable properties, including improved mechanical strength, controlled release profiles, and increased biocompatibility [36, 37]. Personalized medicine is where microphase-separated hydrogels find the most promising applications [38–40]. Recently, PIMS materials were used to successfully form vascular structures with cells *in vitro* [41]. Phase separated hydrogels based on PVA were also used for spinal cord repair [42]. Efforts are also made in the 3D bio-printing with phase separated materials. Application of this technique allowed for in situ formation of stem cell spheroids within 3D printed biomaterial [43].

In acrylate-based hydrogels, separation most often occurs in systems

containing at least two monomers, one of which is hydrophilic and the other one is hydrophobic, and it is not necessary for any of the monomers to be ionic [44,45]. The influence of various types of anions on the separation phenomenon is not well studied, and the few reports focus rather on common inorganic anions, not necessarily associated with the polymer, but e.g. present in the medium (aqueous solution). For example, the influence of sodium chloride concentration on the change of mechanical properties of a hydrogel based on poly(2-hydroxyethyl methacrylate) was studied [46]. Similar studies were carried out for poly(acrylic acid) copolymers, which were swollen with solutions of halogen salts (chloride, bromide and iodide, respectively) [47]. It was observed in them that in solutions of chloride salts the phase separation phenomenon does not occur, while it is more likely in the presence of bromides and even more so iodides, which may suggest that the size of the anion may play a significant role here. An interesting result was the finding that in hydrogels based on ionically cross-linked ampholytes, phase separation occurs at lower NaCl concentrations [48], whereas in the previously mentioned acrylates it occurred at higher concentrations [46,47].

Full control over the PIMS process, despite progress in research, still needs overcoming several challenges. First of all, it is difficult to obtain precise control over the separated domains, their size and distribution in the hydrogel. Competing phase separation and formation of polymer network that occur simultaneously during polymerization often lead to a very heterogeneous structure, both at macro- and micro-level [49].

The following work focused on the creation of new hydrogels based on poly(meth)acrylates modified with sugar acids (namely lactobionic acid). It is worth mentioning here that lactobionic acid is a common sugar acid, which is used as a food supplement. In addition, it occurs in the structure of some drugs, such as erythromycin. The most interesting applications also include its use in solutions for transporting organs, such as Viaspan® [50] or CoStorSol® [51], in which it plays the role of osmotic support and prevents cell swelling. So far, there have been no studies specifically examining the influence of sugar acid anions bound to synthetic polymers on the properties of hydrogels formed from them. It is worth mentioning, however, that sugar acids are components of polymers of biological origin, such as hyaluronic acid [52–54] or alginate [55,56]. These polymers are often used to create hydrogels, some of which also undergo phase separation [57]. However, in this context, it is necessary to distinguish here that in both hyaluronic acid and alginate, it cannot be said that only the carboxylate anions present in them affect phase separation. Among the factors influencing this phenomenon, one can also mention the secondary structure [58] of these polymers and the tendency to self-organize in the presence of various solvents or incompatible polymers [59]. Therefore, the behaviour of such materials is difficult to compare to that described in this work.

The modification was carried out on a commercially available ionic methacrylate by ionic exchange of chloride anion with carboxylate. Then, the new monomer was used for UV triggered copolymerization with 2-hydroxyethyl acrylate (HEA) and bisacrylamide crosslinker in the presence of water, what led to a series of hydrogels with gradually changing mechanical and thermal properties. The obtained materials were compared with those that were created on the basis of commercial monomers, which allowed to confirm the influence of lactobionate anion on the hydrogel properties. Contrary to expectations based on the fact that both ionic monomers dissolve perfectly in water, a clear hydrophobicity was observed in the presence of the one bonded with lactobionate during the polymerization, which manifested as the loss of transparency of the hydrogels after photo-curing. Further research confirmed the occurrence of phase separation by means of atomic force
microscopy and the impact of this phenomenon on the mechanical and
thermal properties of hydrogels was confirmed.

## 2. Results and discussion

Monomers endowed with an electric charge offer a simple way of modification by replacing an anion or cation. This work used commercially available 2-trimethylammonioethyl methacrylate chloride (TMAEMA/Cl) and a two-stage exchange of chloride anion for lactobionate was carried out. This method allows to easily introduce sugar structures into a polymer, which further makes it easy to obtain new, previously inaccessible biological, but also physicochemical properties.

The monomer TMAEMA/Lac (Fig. 1) was prepared as white solid, with good yield of 60 % and characterized using NMR spectroscopy (Supporting information). Then it was used in a process of UV light triggered free-radical copolymerization with the participation of HEA, N,N'-methylenebisacrylamide and 2-hydroxy-2-methylpropiophenone as the photoinitiator. Due to the low solubility of the TMAEMA/Lac in other monomers, it was necessary to use water as a solvent, while maintaining a 1:1 wt ratio of water to monomers. The reaction was carried out in molds of 1x2x0.08 cm with an irradiation with 365 nm light over 30 min. Two hydrogel series were obtained, one based on TMAEMA/Lac and the other based on a commercial TMAEMA/Cl with the same molar ratios of monomers, they were swollen in deionized water and their properties were compared. Since the crosslinked hydrogels are not able to dissolve, their analysis is difficult. For that reason they were dried and their chemical properties were confirmed by means of FT-IR analysis (see Supporting information, Figure S2) which confirmed the presence of typical absorption bands, characteristic for polymethacrylates. Namely 1718 cm⁻¹ for carbonyl bond and 2949 cm⁻¹ for C-C bond in polymer backbone. In all samples a broad band at 3393 cm⁻¹ originates from residual water, thus it is impossible to assign it to OH bonds. Furter, all samples show bands at 1428 cm⁻¹ and 1165 cm⁻¹ which correspond to CH bond (from methyl group) and C-O-C bond respectively. Samples A, B and C show bands at 900 cm⁻¹ which can be assigned to OH groups from tertiary alcohol, which most likely originate from the lactobionate anion.

At first glance, the differences in both series of hydrogels could be observed macroscopically. While the gels based on TMAEMA/Cl exhibited a significant swelling, which could be observed through a significant increase in volume, this phenomenon was not observed to the same extent in the case of the TMAEMA/Lac series. In addition, the lactobionate series also showed loss of transparency, which deepened with the increase in the participation of the monomer containing the sugar anion. As can be seen on the Fig. 2A, the sample with the highest TMAEMA/Lac ratio is fully opaque, while the one with the smallest

amount of this monomer is still transparent.

Basic tests were carried out to determine the swelling ratio (Fig. 2B). In both series, it turned out that this value increases with the increase in the participation of an ionic monomer in the polymer, but these values are much higher for the TMAEMA/Cl series. Obtained results are surprising, because both the chloride and lactobionate monomer dissolve perfectly in water. The same is true for lactobionic acid itself. Possible explanation of that discrepancy might be the phase separation that would cause additional densification of the network by aggregation/precipitation of some parts of the network (for example the polymer backbones) [60]. Similar behaviour was already observed in PEDOT:PSS based materials [61]. As already mentioned, some of the hydrogels obtained in a series with lactobionate turned out to be losing transparency during polymerization (Fig. 2A), although the reaction mixture itself was transparent. Based on these observations, it was hypothesized that in the presence of lactobionic acid, microphase separation may occur, most likely due to the precipitation of polymer chains, and as a consequence the creation of hydrophobic domains. This could explain lower values of swelling ratio than in the case of the chloride series. It is worth emphasizing here that this process would occur during polymerization, i.e. we would deal with polymerization induced microphase separation (PIMS). Similar results were reported previously for polyacrylamides, where the phase separation was induced by phosphate modified sugars [62]. Table 1

To confirm that this phenomenon is actually occurring, samples were analysed using atomic force microscopy (AFM). The swelled hydrogel samples were tested in tapping mode, and the received phase images were presented on Fig. 2E-G. As can be seen, a clear phase separation may actually be observed, especially in the case of a *sample C* (Fig. 2G), which has the highest content of TMAEMA/Lac. This phenomenon can be visible to some extent in the case of *sample B* (Fig. 2F), but in the case of *sample A* (Fig. 2E) it cannot be confirmed. Here, unlike the above-mentioned results, the phase image follows the topographic image of the sample (Supporting information, Figure S3). The analysis was also carried out for samples from the chloride series (Supporting information, Figure S4). Here no separation could be observed, even in the case of the highest participation of ionic monomer. This allows to confirm that the presence of lactobionate causes the phenomenon to occur.

In order to confirm the hypothesis that the precipitating poly(meth) acrylate backbones were the cause of the separation, an attempt was made to analyse the samples using Raman spectroscopy. For this purpose, random locations in the sample were selected and scanned using a 785 nm wavelength. At the same time, it is worth mentioning here that the samples were sensitive to laser light and analysis was not

possible using shorter wavelengths due to burning. As confirmed by the obtained spectra, two types of zones can be distinguished in the

<figure><img src="image_4.png" /><figcaption>**Fig. 1.** Two step synthesis of TMAEMA/Lac via anion exchange and neutralization of OH- anion.</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>**Fig. 2.** Picture showing comparison of obtained hydrogels (A). Swelling ratios of obtained hydrogels (B). Bending of *sample A* (C) and elongation of *sample C* (D). AFM images of *sample A*, scale −10–50 deg (E) *sample B*, scale −25–30 deg (F) and *C*, scale 15–45 deg (G).</figcaption></figure>

<table><caption>**Table 1**

Characteristics of obtained hydrogels.</caption><thead><tr><th>Sample</th><th>Anion</th><th>Molar ratio of TMAEMA to HEA</th><th>Weight ratio of TMAEMA to HEA</th><th>Swelling ratio (%)</th><th>Opacity of the sample</th></tr></thead><tbody><tr><td>A</td><td>Lac</td><td>0.066</td><td>1:3</td><td>327 ± 7</td><td>no</td></tr><tr><td>B</td><td></td><td>0.11</td><td>1:2</td><td>536 ± 9</td><td>yes</td></tr><tr><td>C</td><td></td><td>0.17</td><td>1:1</td><td>768 ± 81</td><td>yes</td></tr><tr><td>D</td><td>Cl</td><td>0.066</td><td>1:8</td><td>1037 ± 14</td><td>no</td></tr><tr><td>E</td><td></td><td>0.11</td><td>1:4.5</td><td>1140 ± 95</td><td>no</td></tr><tr><td>F</td><td></td><td>0.17</td><td>1:2.5</td><td>1180 ± 30</td><td>no</td></tr></tbody></table>

sample. Namely, these are zones in which differences in the ratio of modes at 1456 cm⁻¹ and the broad mode at 1365 cm⁻¹ can be clearly identified (Fig. 3). The first of them can be attributed to the bending mode of the -CH₃ groups [63], which in the tested hydrogel are present only in the polymer backbone. In turn, the other mode consists of signals originating from different modes, of which the stretching C-O and O-H modes can be distinguished [64]. Such functional groups are found both in the lactobionate anion, rich in hydroxyl groups, and in the HEA comonomer present in this system. Their high polarity rather indicates increased hydrophilicity. It can be clearly indicated on this basis that there are hydrophilic and hydrophobic zones in the hydrogel. At the same time, zones richer in -CH₃ groups, to which hydrophobicity is

assigned, are poorer in -C-OH groups and conversely, zones rich in hydroxyl groups, to which hydrophilicity is assigned, are poorer in methyl groups. It is worth mentioning that the hydrophobic zones are additionally richer in modes originating from C-H stretching mode (1086 cm⁻¹) [65] and ester carbonyl groups (1730 cm⁻¹) [65], which both are closely bonded to the polymer backbones. Hydrophilic zones seem richer in broad 1656 cm⁻¹ modes, which possibly originate from acid carbonyl moieties [66]. This type of functional groups is present only in lactobionic acid, which due to its polarity should indicate hydrophilicity. Further, the broad mode at 3280 cm⁻¹, which corresponds to stretching modes for hydroxyl groups [67], was analysed. Here too, it was confirmed that this mode is more pronounced for zones previously defined as hydrophilic. Based on the above presented results, it can be said that the phase separation, confirmed by AFM, is caused by the lack of compatibility between the polymer backbone and the lactobionate unit. It is worth emphasizing here that it cannot be directly indicated that this is due only to the hydroxyl groups present in lactobionic acid, because they are also present in the HEA monomer. As mentioned earlier, separation was not observed in the case of hydrogels with chloride anion, in which 2-hydroxyethyl acrylate was also present. It is also worth noting that both -C-OH and -CH₃ groups are present in both hydrophilic and hydrophobic zones. The conclusion that can be drawn from the presented results is that the ionic units containing the lactobionate anion present in *samples A-C* may exhibit significantly greater polarity than the TMAEMA/Cl monomer. This is due to the fact that, in
<figure><img src="image_6.png" /><figcaption>**Fig. 3.** Raman spectra showing different hydrophilic and hydrophobic zones detected on sample C.</figcaption></figure>

addition to the ammonium cation-anion pair, lactobionate contains multiple hydroxyl groups. This allows these units to bind water much more effectively (e.g., electrostatically), but interactions between the corresponding lactobionic acid units may also occur. This may, in a sense, resemble additional cross-linking and the formation of water-rich hydrophilic zones. This, in turn, may lead to the formation of hydrophobic zones, the main component of which are polymeric backbones. When the concentration of hydrophilic zones is sufficient (with increasing lactobionic acid content), a sufficient number of hydrophobic zones are formed that they can separate or even precipitate [68]. This, in turn, may result in changes, for example, in the refractive index, which we observe as a loss of transparency. Although in the case of the tested sample, separation can be clearly stated, it does not mean that all the backbones or all the hydroxyl groups are subject to it. This is due to the fact that the tested system is cross-linked, and therefore the polymer components do not have full freedom of movement and are limited by the cross-linking agent. For this reason, we will always have to deal with the presence of both types of functional groups in all the zones.

For comparison, the chloride containing **sample F** was tested by means of Raman spectroscopy (spectrum showed in the **Supplementary Information, Figure S9**). There were no different phases detected here and the spectra taken on different spots look the same. It can be seen that all the modes that were present on the spectrum of lactobionate containing sample are present here too. It is necessary to point out though that the intensities of the modes and proportions between them are different. Most importantly, the mode at 1365 cm⁻¹, which were assigned to stretching of C-O and O-H groups, and mode at and 1456 cm⁻¹, previously assigned to CH₃ groups, exhibit very similar intensities, to the “hydrophobic zone” on lactobionate spectrum (Fig. 3). This can suggest that although there are methyl groups present everywhere, we have a lot less hydroxyl groups present in each zone. This is due to the lack of hydroxyl rich lactobionate anion and all other hydroxyls originating only from the HEA monomer. Additionally, the broad mode at 3280 cm⁻¹ has intensity similar to the one on the

spectrum of hydrophilic phase. Based on that we can claim that there is no phase separation present for the **sample F**, and thus, the amount of water in each tested zone was more or less the same.

After confirming and analysing the phase separation occurring in the system, the obtained hydrogels were subjected to rheological and thermal analysis to determine the properties of the hydrogels and to check the influence of the phenomenon described above on them. The rheological measurements (amplitude sweep, Fig. 4A,B) show that viscoelastic region increases with the increase in the lactobionate anion fraction. This range is extended to approximately 30% (**sample A**), 200% (**sample B**) and 300% (**sample C**), respectively. The flow points (when G' and G'' curves cross each other), follow the same trend, namely increase in the order **sample A** (200%) < **sample B** (300%) < **sample C**, which is interestingly over 1000%. For **sample A** and **sample B**, an abrupt decrease of G' in observed at these flow points, as it was observed for the chloride series meaning that the hydrogel structure breaks. Conversely, **sample C** show a different behaviour with a very progressive decrease of G' and G'', evidencing that this material would last until 1000% of deformation. This can also be observed macroscopically, namely, when the obtained materials were bent, all samples from the chloride series shattered and broke in a similar way as would happen in the case of glass. In contrast, in the second series, the obtained hydrogels can be bent and stretched, with **sample C** showing the greatest elasticity (Supporting information, Figure S8). It is also worth noting here the relationship in which the increase in the linear viscoelastic range corresponds to a decrease in the material stiffness. Acid functionalized sugars were recently reported to influence rheological properties of hydrogels [62]. With the increased sugar content described materials were softer, but at the same time they showed to be more elastic and able to extend significantly.

Further studies focused on the analysis of thermal properties. First of all, thermogravimetric analysis of lyophilized samples was performed (Fig. 5). Here, a clear difference in the course of xerogel decomposition between the series can be seen. First of all, while in the case of the chloride series we can see a clear two-stage thermal decomposition of the samples, in the lactobionate series the decomposition appears to be two-stage with mild first transition starting at 180°C followed by abrupt decomposition at 400–450°C. The temperature of the first step is very typical for sugars and corresponds to the caramelization [69]. Although the decomposition temperature of lactobionic acid was not reported to date, similar sugars were already analysed, for example glucose caramelisation begins at 185°C [70], and lactose at 224°C [71]. In our test, lactobionic acid decomposition also occurs at elevated temperature with onset at 290°C (see Supporting information, Figure S7). It is worth noting that the process corresponding to caramelization in studied xerogels is most pronounced for the **sample C**, where the percentage of TMAEMA/Lac monomer is the highest. However, no clear decomposition can be seen, that could be assigned to first stage of decomposition of polymer, clearly visible for chloride series. This result is quite surprising and suggests that the presence of lactobionate increases the thermal resistance of the polymer. The phenomenon of increasing thermal stability of synthetic polymers by sugars is not widely known, which results from the fact that the use of these biomolecules in macromolecular chemistry is still quite new. However, the phenomenon of increasing protein stability in the presence of sugar is known and applied for many food and pharmaceutics applications [72–75]. It has also been proven that disaccharides like trehalose show the highest efficiency in protecting proteins from thermal denaturation [76]. It is possible that sugar acids, including lactobionic acid, may show a similar effect.

To better understand the thermal decomposition of the proposed materials, activation energies (Ea) were calculated for temperature ranges selected based on dTGA. A modified form of the Coats and Redfern model was used for this purpose [77–80]. The calculated values are presented in Table S1 (see Supporting Information). Based on the obtained values, it can be clearly concluded that the decomposition of the hydrogels described here occurs via non-spontaneous endothermic
<figure><img src="image_7.png" /><figcaption>**Fig. 4.** Rheological analysis of fully swelled hydrogels. Amplitude sweep experiments for lactobionate (A) and chloride (B) series. Frequency sweep experiments for lactobionate (C) and chloride (D) series.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Fig. 5.** Thermogravimetric analysis (TGA) and first derivative (dTGA) of freeze-dried hydrogels for lactobionate series (top) and chloride series (bottom).</figcaption></figure>

Furthermore, the $E_a$ values are typical for hydrogels based on polymer structures [81–83]. However, it is worth emphasizing a clear difference between the series of chloride and lactobionate hydrogels. The former decomposed in two stages, the first of which (in the 200–350°C range) was characterized by a higher $E_a$ value, while the second (in the 390–450°C range) was characterized by a lower $E_a$ value.

This may indicate that after the first stage, the residues decompose more readily in the second stage. In the case of the lactobionate series, with the exception of **sample C**, these hydrogels disintegrated in a single step (using dTGA). **Sample C** behaved similarly to the chloride series, likely due to the significant number of lactobionate units, a sugar that could trigger an additional process. It is worth noting that the $E_a$ values are lower than for the chloride series, at least for the first stage of decomposition. Comparing only the second stage for the chloride series (in the range of 390–450°C), the values obtained for the lactobionate series are very similar (41–44 kJ/mol for chlorides and 40–53 kJ/mol for lactobionates).

In further studies, attention was paid to DSC analysis to check whether and how the presence of sugar anion affects the glass transition temperature of the polymer. For this purpose, freeze-dried samples were tested in the temperature range from –50–150°C. From the thermograms shown (Supporting information, Figure S5), it can be seen that the chloride xerogels show a clear increasing trend of $T_g$ with the ionic monomer content. In the case of the lactobionate series, this trend is not as clear and it can be said that the glass transition temperatures for all three polymers are very similar. Again, the effect of sugars on the thermal properties of synthetic polymers is not well studied, but the research on the effect of the presence of sugars on the properties of biopolymers such as proteins and polysaccharides is more available. For example, it has been found that the presence of elevated fructose concentrations can lead to casein plasticization [84]. In general, the presence of sugars leads to a decrease in the $T_g$ for dry biopolymers [85–87]. Also in the case of the hydrogels obtained here, a decrease in the glass transition temperature can be observed, especially when comparing **samples C** and **F**. Recently it was reported, that hydrogels with sugar based phytic acid exhibited lower $T_g$, what was caused by weakened intramolecular interaction between polymer chains and increased free volume introduced by the sugar [62].

The last analysis performed was the morphology analysis using
scanning electron microscopy. Freeze-dried samples of all hydrogels were analysed, which allowed to investigate the effect of lactobionate on the porosity of the hydrogels. As can be seen in Fig. 6 and Supporting information Figure S6, hydrogels containing sugar anions appear more compact and do not show high porosity. In contrast, chloride hydrogels are porous and may resemble a sponge. This result corresponds to the swelling results. The series of lactobionate hydrogels swelled to a much lesser extent than the series based on TMAEMA/Cl monomer. Due to this, the pores of these materials are also smaller and harder to observe.

# 3. Materials and methods

## 3.1. Materials

2-hydroxyethyl acrylate (HEA), N,N'-methylenebisacrylamide, 2-tri-methylammonioethyl methacrylate chloride (TMAEMA/Cl) and 2-hydroxy-2-methylpropiophenone were purchased from Tokyo Chemical Industries. Lactobionic acid was purchased from Fluorochem. Amberlite® IRN-78 ion-exchange resin was obtained from Thermo Scientific. HPLC grade methanol was obtained from Sigma Aldrich. TMAEMA/Cl which is sold as 80 % aqueous solution was dried on the rotavap before further use.

## 3.2. Lactobionic acid containing monomer (TMAEMA/Lac) preparation

Commercially available TMAEMA/Cl monomer (10 g, 48,1 mmol) was placed in a round-bottomed flask and dissolved in 250 mL of methanol. Then 3 g of ion exchange resin was added. The mixture was stirred overnight. The mixture was then filtered and the solvent was evaporated. The dark yellow liquid thus obtained (7289 g; 38,5 mmol) was dissolved in water (100 mL), and then lactobionic acid (13,8 g, 38,5 mmol) was added. The resulting solution was stirred again overnight and then the water was evaporated using a rotary evaporator. 12,22 g was obtained, yield 60 %.

## 3.3. General procedure for synthesis of hydrogels (both chloride and lactobionate)

Monomers in appropriate ratios (98 % weight), N,N'-methylenebisacrylamide (1 % weight), 2-hydroxy-2-methylpropiophenone (1 % weight) (5 g in total) and water (5 g, 5 mL) were mixed in a falcon tube and sonicated (the total mass of obtained resin was 10 g). Then, the obtained solution was transferred to molds, covered with a lid and irradiated with UV light (365 nm) for 30 min.

# 4. Methods

## 4.1. Swelling ratio measurements

Freeze-dried gels were placed into water until fully swelled (24 h)

and the swelling ratio was calculated as follows:

$$SR = \frac{m_s - m_d}{m_d} \times 100\%$$

Where: SR is swelling ratio, m_s is mass of swelled gel, m_d is mass of dry gel. All experiments were performed in triplicate.

## 4.2. Nuclear magnetic resonance

¹H- and ¹³C NMR spectra were obtained at 298 K in DMSO-d6 as internal reference and were recorded on a Bruker Avance 400 spectrometer. Chemical shifts are reported in parts per million (ppm).

## 4.3. Fourier transformation infrared spectroscopy

Fourier transformation infrared spectra of freeze-dried hydrogels were collected using PerkinElmer Frontier FTIR/FIR instrument equipped with a ATR in a range of 4000–600 cm⁻¹ at a resolution of 0.125 cm⁻¹ and 16 scans.

## 4.4. Atomic force microscopy

AFM images were collected using a Smart SPM-1000 AIST-NT microscope. Images were acquired in tapping mode (resonance frequency: 325 kHz) with a silicon tip (MikroMasch HQNSC15/AIBS).

## 4.5. Raman spectroscopy

Raman spectra were collected using XPLORA-HORIBA-JOBIN YVON spectrometer. Excitation was achieved with a 785 nm laser line focused on the sample with a microscope objective (x100) and a power of 30 mW.

## 4.6. Rheology

The rheological properties of the hydrogels have been measured with a MCR301 Anton Paar rheometer. The geometry is a stainless steel plate as the lower plate and a disposable sandblasted stainless steel plate (diameter 8 mm) as the upper plate. A normal force of 1 N is applied to ensure a good contact between the sample and the plates. Then the frequency sweep has been recorded from 10 to 0.1 Hz at a shear strain of 0.2 % and at 37°C. Also, to determine the linear viscoelastic region, the shear strain is varied from 0.1 % to 1000 % at 37°C and at a frequency of 1 Hz

## 4.7. Differential scanning calorimetry

DSC thermograms were acquired using a Netzsch DSC 3500

Syrius instrument with a heating/cooling ramp of ±10 °C/min and a nitrogen gas purge of 20 mL/min. Temperature and enthalpy has been

<figure><img src="image_9.png" /><figcaption>Fig. 6. SEM images of lactobionate containing xerogel, sample A (A) and chloride containing xerogel, sample E (B) showing clear difference in porosity.</figcaption></figure>
calibrated using the melting transition of indium.

## 4.8. Thermogravimetric analysis

Thermogravimetric thermograms were acquired on a Mettler-Toledo TGA/DSC3 + with a heating ramp of 10 °C/min from room temperature to 600°C. Temperature has been calibrated using the melting transition of indium, zinc and aluminium.

## 4.9. Scanning electron microscopy

SEM images were acquired using a JEOL JSM-7800F Prime microscope from the R. Castaing micro-characterization platform.

# 5. Conclusions

Above presented study explains a straightforward, anion-exchange strategy to modify charged monomers, successfully replacing chloride with lactobionate in TMAEMA to introduce sugar moieties into hydrogels. The synthesized TMAEMA/Lac monomer was copolymerized with HEA via UV-initiated free-radical polymerization, yielding two hydrogel series with distinct properties.

The presence of the common sugar acid unit significantly influenced the properties of the obtained materials. TMAEMA/Lac hydrogels exhibited lower swelling ratios (max 768 %) compared to TMAEMA/Cl (1180 %) and attributed to polymerization-induced microphase separation (PIMS). AFM and Raman spectroscopy identified hydrophobic (polymer backbone-rich) and hydrophilic (lactobionate-rich) domains, explaining opacity in TMAEMA/Lac hydrogels. This phenomenon, absent in chloride-based gels, suggests lactobionate's role in driving network densification.

The significant effect of the lactobionic anion on the mechanical properties of the hydrogels was confirmed by rheological tests, in which the samples containing units endowed with this anion showed greater resistance to strain (over 1000 % strain for the sample with the highest lactobionate content) while the hydrogels with the chloride anion underwent the brittle fracture under the 100 % strain.

Thermal properties of the materials also differed by means of TGA, which revealed improved thermal resistance in lactobionate-modified xerogels, with decomposition shifted to 400–450°C, while DSC indicated reduced Tg, suggesting sugar-mediated plasticization.

The study underscores the potential of sugar-based anion exchange to tailor hydrogel properties, offering a versatile platform for designing biomaterials with tuneable mechanical, thermal, and morphological features. Future work could explore applications in drug delivery or tissue engineering, leveraging lactobionate's biocompatibility and the unique PIMS-driven microstructure.

## Author contributions

R. Bielas planned the experiments and designed the materials, obtained monomer, all the hydrogels, performed NMR and FT-IR analysis. M. Tassé performed AFM and Raman measurements and analysis. J. Fitremann performed rheological measurements. B. Martin performed DSC and TGA measurements. V. Collière performed SEM analysis. Gabor Molnar, Lionel Salmon and Azzedine Bousseksou analysed the data. All authors contributed to the analysis and interpretation of the data. R. Bielas wrote the manuscript.

## CRediT authorship contribution statement

**Rafal Bielas:** Writing – original draft, Visualization, Supervision, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. **Marine Tassé:** Visualization, Methodology, Investigation. **Juliette Fitremann:** Writing – original draft, Methodology, Investigation, Data curation. **Baptiste Martin:** Investigation. **Vincent Collière:**

Investigation. **Gabor Molnar:** Supervision. **Lionel Salmon:** Supervision. **Azzedine Bousseksou:** Supervision.

## Conflicts of interests

There are no conflicts to declare.

## Supporting information

* ¹H and ¹³C NMR spectra of each step in the monomer synthesis; FT-IR spectra of freeze-dried hydrogels; topography AFM images of TMAEMA/Lac containing hydrogels; phase AFM image of example of TMAEMA/Cl containing hydrogel; DSC thermograms for all the hydrogels; SEM images of hydrogels, TGA thermogram for lactobionic acid; images of all obtained hydrogels showing how they bend when tilted.

## Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Acknowledgements

The authors are grateful to prof. Barbara Hachula from the University of Silesia, Katowice, for the help with the chloride Raman spectra.

## Appendix A. Supporting information

Supplementary data associated with this article can be found in the online version at doi:10.1016/j.colsurfa.2025.138126.

## Data Availability

Data will be made available on request.

## References

[1] P. Calvert, Hydrogels for soft machines, Adv. Mater. 21 (7) (2009) 743–756.

[2] W.A. Laftah, S. Hashim, A.N. Ibrahim, Polymer hydrogels: a review, Polym. Plast. Technol. Eng. 50 (14) (2011) 1475–1486.

[3] C. Cui, Q. Fu, L. Meng, S. Hao, R. Dai, J. Yang, Recent progress in natural biopolymers conductive hydrogels for flexible wearable sensors and energy devices: materials, structures, and performance, ACS Appl. Bio Mater. 4 (1) (2021) 85–121.

[4] R. Messing, A.M. Schmidt, Perspectives for the mechanical manipulation of hybrid hydrogels, Polym. Chem. 2 (1) (2011) 18–32.

[5] J.L. Holloway, A.M. Lowman, G.R. Palmese, The role of crystallization and phase separation in the formation of physically Cross-Linked PVA hydrogels, Soft Matter 9 (3) (2013) 826–833.

[6] N.A. Peppas, J.Z. Hilt, A. Khademhosseini, R. Langer, Hydrogels in biology and Medicine: from molecular principles to bionanotechnology, Adv. Mater. 18 (11) (2006) 1345–1360.

[7] C.A. Dreiss, Hydrogel design strategies for drug delivery, Curr. Opin. Colloid Interface Sci. 48 (2020) 1–17.

[8] J. Li, D.J. Mooney, Designing hydrogels for controlled drug delivery, Nat. Rev. Mater. 1 (12) (2016) 16071.

[9] B.V. Slaughter, S.S. Khurshid, O.Z. Fisher, A. Khademhosseini, N.A. Peppas, Hydrogels in regenerative Medicine, Adv. Mater. 21 (32–33) (2009) 3307–3329.

[10] C. Liaw, S. Ji, M. Guvendiren, Engineering 3D hydrogels for personalized in vitro human tissue models, Adv. Healthc. Mater. 7 (4) (2018) 1701165.

[11] M.E. Sagsoz, O. Korkut, S. Gallo, Advancements in tissue-equivalent gel dosimeters, Gels 11 (2) (2025) 81.

[12] F. Hashemi-Afzal, H. Fallahi, F. Bagheri, M.N. Collins, M.B. Eslaminejad, H. Seitz, Advancements in hydrogel design for articular cartilage regeneration: a comprehensive review, Bioact. Mater. 43 (2025) 1–31.

[13] C. Lai, W. Chen, Y. Qin, D. Xu, Y. Lai, S. He, Innovative hydrogel design: tailoring immunomodulation for optimal chronic wound recovery, Adv. Sci. 12 (2) (2025) 2412360.

[14] Md.M.H. Rumon, Md.S. Rahman, A.A. Akib, Md.S. Sohag, Md.R.A. Rakib, Md.A. R. Khan, F. Yesmin, M.S. Shakil, M.M. Rahman Khan, Progress in hydrogel toughening: addressing structural and crosslinking challenges for biomedical applications, Discov. Mater. 5 (1) (2025) 5.
[15] Y. Liu, L. Si, Y. Jiang, S. Jiang, X. Zhang, S. Li, J. Chen, J. Hu, Design of pH-Responsive nanomaterials based on the tumor microenvironment, *IJN* 20 (2025) 705-721.

[16] S. Bian, H. Ye, P. Wang, C. Li, X. Guo, M. Guan, S. Feng, Antibacterial hydrogel: the sniper of chronic wounds, *BMEMat* (2025) e241501.

[17] K. Zhang, K. Xue, X.J. Loh, Thermo-Responsive hydrogels: from recent progress to biomedical applications, *Gels* 7 (3) (2021) 77.

[18] I.S. Protsak, Y.M. Morozov, Fundamentals and advances in Stimuli-Responsive hydrogels and their applications: a review, *Gels* 11 (1) (2025) 30.

[19] Y. Yang, Y. Ru, T. Zhao, M. Liu, Bioinspired multiphase composite gel materials: from controlled Micro-Phase separation to multiple functionalities, *Chem* 9 (11) (2023) 3113–3137.

[20] J. Brijitta, P. Schurtenberger, Responsive hydrogel colloids: structure, interactions, phase behavior, and equilibrium and nonequilibrium transitions of microgel dispersions, *Curr. Opin. Colloid Interface Sci.* 40 (2019) 87–103.

[21] Y. Du, J. Zeng, Q. Sun, S. Yu, D. Yang, S. Huang, Polymerization-Induced highly brilliant and Color-Recordable mechanochromic photonic gels for Ink-Free patterning, *J. Colloid Inter. Sci.* 679 (2025) 883–892.

[22] H. Jeong, J. Gu, P. Mwasame, K. Patankar, D. Yu, C.E. Sing, The effect of selective surface interaction on polymer phase separation with explicit polydispersity during polymerization, *Soft Matter* 21 (2025) 1308–1322.

[23] Y. Li, F. Liu, S. Demirci, U.K. Dey, T. Rawah, A. Chaudary, R. Ortega, Z. Yang, E. Pirhadi, B. Huang, Y. Xong, S. Jiang, Two sides of the coin: synthesis and applications of janus particles, *Nanoscale* 17 (1) (2025) 88–112.

[24] X.N. Zhang, C. Du, Z. Wei, M. Du, Q. Zheng, Z.L. Wu, Stretchable Sponge-like hydrogels with a unique colloidal network produced by Polymerization-Induced microphase separation, *Macromolecules* 55 (4) (2022) 1424–1434.

[25] B.M. Bailey, R. Fei, D. Munoz-Pinto, M.S. Hahn, M.A. Grunlan, PDMSTAR-PEG hydrogels prepared via Solvent-Induced phase separation (SIPS) and their potential utility as tissue engineering scaffolds, *Acta Biomater.* 8 (12) (2012) 4324–4333.

[26] F. Abedin, Q. Ye, H.J. Good, R. Parthasarathy, P. Spencer, Polymerization- and Solvent-Induced phase separation in Hydrophilic-Rich dentin adhesive mimic, *Acta Biomater.* 10 (7) (2014) 3038–3047.

[27] D. Ehrhardt, J. Mangialetto, K. Van Durme, B. Van Mele, N. Van Den Brande, From slow to fast Self-Healing at ambient temperature of High-Modulus reversible Poly (Methacrylate) networks. Single- and Dual-Dynamics and the effect of phase separation, *Macromolecules* 54 (21) (2022) 9960–9977.

[28] K.R. Han, A. Saddique, J. Lyu, J.C. Kim, I.W. Cheong, Microphase separation effects on surface Scratch-Healing and Thermo-Mechanical properties of Self-Healing copolymers with dynamic covalent bonds, *ACS Appl. Polym. Mater.* 6 (13) (2024) 7512–7523.

[29] Y. Yang, D. Davydovich, C.C. Hornat, X. Liu, M.W. Urban, Leaf-Inspired Self-Healing polymers, *Chem* 4 (8) (2018) 1928–1936.

[30] Y. Luo, Y. Qian, M. Cai, P. Zhang, J. Li, Z. Luo, J. Hu, Y. Li, Q. Zhang, X. Ren, Polar groups promoting In-Situ polymerization phase separation for solid electrolytes enabling Solid-State battery batteries, *J. Coll. Inter. Sci.* 678 (2025) 53–62.

[31] D. Saha, C.L. Witt, R. Fatima, T. Uchiyama, V. Pande, D.-P. Song, H.-F. Fei, B. M. Yavitt, J.J. Watkins, Opportunities in bottlebrush block copolymers for advanced materials, *ACS Nano* 19 (2) (2025) 1884–1910.

[32] T. Oh, S. Cho, C. Yoo, W. Yeo, J. Oh, M. Seo, Polymerization-induced microphase separation of a polymerization mixture into nanostructured block polymer materials, *Prog. Polym. Sci.* 145 (2023) 101738.

[33] M. Rong, S. Ma, P. Lin, M. Cai, Z. Zheng, F. Zhou, Polymerization induced phase separation as a generalized methodology for Multi-Layered hydrogel tubes, *J. Mater. Chem. B* 7 (22) (2019) 3505–3511.

[34] S. Guo, G. Kang, D.T. Phan, M.N. Hsu, Y.C. Por, C.H. Chen, Polymerization-Induced phase separation formation of structured hydrogel particles via microfluidics for scar therapeutics, *Sci. Rep.* 8 (1) (2018) 2245.

[35] A. Nishiguchi, E. Araki, D. Palai, S. Ito, T. Taguchi, Development of Phase-Separating microfiber network hydrogels to promote in vitro vascularization, *Biomacromolecules* 25 (9) (2024) 6146–6154.

[36] G. Liu, S. Li, B. Deng, L. Huo, H. Bai, S. Jiang, Y. Zhou, Z. Pei, C. Kimna, Y. Zhao, L. Xu, J. Li, X. Mu, J. Song, Phase-Separated anisotropic PVA hydrogel loaded with tetramethylpyrazine for spinal cord injury repair, *Chem. Eng. J.* 506 (2025) 159944.

[37] S. Zhu, X. Liao, Y. Xu, N. Zhou, Y. Pan, J. Song, T. Zheng, L. Zhang, L. Bai, Y. Wang, X. Zhou, M. Gou, J. Tao, R. Liu, 3D bioprinting of High-Performance hydrogel with in-Situ birth of stem cell spheroids, *Bioact. Mater.* 43 (2025) 392–405.

[38] S. Wang, L. Li, D. Su, K. Robin, K.A. Brown, Patterning porosity in hydrogels by arresting phase separation, *ACS Appl. Interfaces* 10 (40) (2018) 34604–34610.

[39] J. Hiltz, M. Trope, Vitality of human lip fibroblasts in milk, hanks balanced salt solution and viaspan storage media, *Dent. Traum* 7 (2) (1991) 69–72.

[40] A. Ostrózka-Cieślik, B. Dollínska, F. Ryszka, Tips for optimizing organ preservation solutions, *Acta Biochim. Pol.* 65 (1) (2018) 9–15.

[41] L. Song, Z. Wang, S. Chen, Y. Shen, J. Yin, R. Wang, Phytic Acid-Induced gradient hydrogels for highly sensitive and broad range pressure sensing, *Adv. Mater.* (2025) 2417978.

[42] A. Abbadessa, M. Landín, E. Oude Blenke, W.E. Hennink, T. Vermonden, Two-Component thermosensitive hydrogels: phase separation affecting rheological behavior, *Eur. Polym. J.* 92 (2017) 13–26.

[43] J.A. Hourigan, E.V. Lifran, L.T.T. Vu, Y. Listohadi, R.W. Sleigh, Lactose: chemistry, processing, and utilization, in: *G.W. Smithers, M.A. Augustin (Eds.), In Advances in Dairy Ingredients*, Wiley, 2013, pp. 21–41.

[44] A. Magon, M. Pyda, Melting, glass transition, and apparent heat capacity of α-d-Glucose by thermal analysis, *Carbohydr. Res.* 346 (16) (2011) 2558–2566.

[45] Strasser, C. Stabilité Thermique Du Lactose Par TGA-TFT-IR, 2022. https://analyzin g-testing.netzsch.com/fr/application-literature/stabilite-thermique-du-lactose-p ar-les-moyens-de-lat-ft-ir (accessed 2025-02-11).

[46] H. Oshima, M. Kinoshita, Effects of sugars on the thermal stability of a protein, *J. Chem. Phys.* 138 (2013) 245101.

[47] A.L. Mateescu, N.-B. Mincu, S. Vasilca, R. Apetrei, D. Stan, B. Zorilă, D. Stan, The influence of Sugar-Protein complexes on the thermostability of C-Reactive protein (CRP), *Sci. Rep.* 11 (1) (2021) 13017.

[48] V. Leung, J. Mapletoft, A. Zhang, A. Lee, F. Vahedi, M. Chew, A. Szewczyk, S. Jahanshahi-Anbuchi, J. Ang, B. Cowbrough, M.S. Miller, A. Ashkar, C.D.M. Filipe, Thermal stabilization of viral vaccines in Low-Cost sugar films, *Sci. Rep.* 9 (1) (2019) 7631.

[49] Y. Huo, X. Hou, Y. Yu, X. Wen, Y. Ding, Y. Li, Z. Wang, Improving the thermal and oxidative stability of Food-Grade phycocyanin from arthrospira platensis by addition of saccharides and sugar alcohols, *Foods* 11 (12) (2022) 1752.

[50] Y. Liang, L. Matia-Merino, H. Patel, A. Ye, G. Gillies, M. Golding, Effect of sugar type and concentration on the heat coagulation of Oil-in-Water emulsions stabilized by Milk-Protein-Concentrate, *Food Hydrocoll.* 41 (2014) 332–342.

[51] M.T. Kalichevsky, J.M.V. Blanshard, P.F. Tokarguz, Effect of water content and sugars on the phase transition of casein and sodium caseinate, *Int J. Food Sci. Tech.* 28 (2) (1993) 139–151.

[52] H. Kumagai, W. MacNaughtan, I.A. Farhat, J.R. Mitchell, The influence of carrageenan on molecular mobility in low moisture amorphous sugars, *Carbohydr. Polym.* 48 (4) (2002) 341–349.

[53] F.A. Momany, J.L. Willett, Molecular dynamics calculations on amylose fragments. I. Glass transition temperatures of maltodecaose at 1, 5, 10, and 15.8% hydration, *Biopolymers* 63 (2) (2002) 99–110.

[54] S. Kasapis, Recent advances and future challenges in the explanation and exploitation of the network glass phase separation of high Sugar/Biopolymer mixtures, *Crit. Rev. Food Sci. Nutr.* 48 (2) (2008) 185–203.

[55] S. Dong, Y. Li, K. Zhu, C. Wang, S. Zhai, Advances in Structure Designing and Function Tailoring Strategy toward Alginate-Based Hydrogels for Efficient Water Remediation, *A Review., International Journal of Biological Macromolecules* 304 (2025) 140801.

[56] P. Tordi, F. Ridì, P. Samori, M. Bonini, Cation-Alginate Complexes and Their Hydrogels: A Powerful Toolkit for the Development of Next Generation Sustainable Functional Materials, *Advanced Functional Materials* 35 (2025) 2416390.

[57] A. Abbadessa, M. Landín, E. Oude Blenke, W.E. Hennink, T. Vermonden, Two-Component Thermosensitive Hydrogels: Phase Separation Affecting Rheological Behavior, *European Polymer Journal* 92 (2017) 13–26.

[58] K.C. Lesco, S.K.R. Williams, L.M.L. Laurens, Marine Algae Polysaccharides: An Overview of Characterization Techniques for Structural and Molecular Elucidation, *Marine Drugs* 23 (3) (2025) 105.

[59] Y. Wang, H. Liu, B. Wang, G. Gheyret, J. Qin, H. Wang, Y. Di, Y. Wang, J. Wang, H. Tan, Recent Advances in the Biosynthesis of Polysaccharide-Based Antimicrobial Glycoconjugate Vaccines, *Front. Microbiol.* 15 (2025) 1457908.

[60] D. Li, Y. Li, X. Zhang, M. Mohan, T. Lei, K. Chen, C. Chia, B. Zhang, Q. Zhang, Y. Wei, Morphological Evolution, Mechanical Properties and Hygroscopicity Behaviour of Hydrogel Fibres, *Sci. China Mater.* (2025).

[61] H. Li, J. Cao, R. Wan, V.R. Feig, C.M. Tringides, J. Xu, H. Yuk, B. Lu, PEDOTs-Based Conductive Hydrogels: Design, Fabrications, and Applications, *Advanced Materials* 37 (7) (2025) 2415151.

[62] L. Song, Z. Wang, S. Chen, Y. Shen, J. Yin, R. Wang, Phytic Acid-Induced Gradient Hydrogels for Highly Sensitive and Broad Range Pressure Sensing, *Advanced Materials* 2417978 (2025).

[63] C.-H. Liu, J. Qi, J. Lu, S. Wang, C. Wu, W.-C. Shih, K.V. Larin, Improvement of Tissue Analysis and Classification Using Optical Coherence Tomography Combined with Raman Spectroscopy, *J. Innov. Opt. Health Sci.* 8 (4) (2015) 1550006.

[64] H.T. Varghese, C.Y. Panicker, D. Philip, IR, Raman and SERS Spectra of 5- sulphosalicylic Acid Dihydrate, *J Raman Spectroscopy* 38 (3) (2007) 309–315.

[65] A. M. Miranda, E. W. Castilho-Almeida, E. H. Martins Ferreira, G. F. Moreira, C. A. Achete, R. A. S. Z. Armond, H. F. Dos Santos, A. Jorio, Line Shape Analysis of the Raman Spectra from Pure and Mixed Biofuels Esters Compounds, *Fuel* 115 (2014) 118–125.

[66] F. Génin, F. Quilès, A. Burneau, Infrared and Raman Spectroscopic Study of Carboxylic Acids in Heavy Water, *Phys. Chem. Chem. Phys.* 3 (6) (2001) 932–942.

[67] S. Ritschar, V.K. Bangalore Narayana, M. Rabus, C. Laforsch, Uncovering the Chemistry behind Inducible Morphological Defences in the Crustacean Daphnia Magna via Micro-Raman Spectroscopy, *Sci Rep* 10 (1) (2020) 22408.

[68] L. Yu, Z. Zhang, J. Ding, Vitro Degradation and Protein Release of Transparent and Opaque Physical Hydrogels of Block Copolymers at Body Temperature, *Macromol. Res.* 20 (3) (2012) 234–243.

[69] J. A. Hourigan, E. V. Lifran, L. T. T. Vu, Y. Listohadi, R. W. Sleigh, Lactose: Chemistry, Processing, and Utilization. In Advances in Dairy Ingredients; G. W. Smithers, M. A. Augustin, Eds.; Wiley, 2013; pp 21–41.

[70] A. Magon, M. Pyda, Melting, Glass Transition, and Apparent Heat Capacity of α-d-Glucose by Thermal Analysis. *Carbohydrate Research* 346 (16) (2011) 2558–2566.

[71] C. Strasser, Stabilité Thermique Du Lactose Par TGA-TFT-IR, 2022. https://analyzin g-testing.netzsch.com/fr/application-literature/stabilite-thermique-du-lactose-p ar-les-moyens-de-lat-ft-ir (accessed 2025-02-11).

[72] H. Oshima, M. Kinoshita, Effects of Sugars on the Thermal Stability of a Protein, *The Journal of Chemical Physics* 138 (2013) 245101.

[73] A.L. Mateescu, N.-B. Mincu, S. Vasilca, R. Apetrei, D. Stan, B. Zorilă, D. Stan, The Influence of Sugar-Protein Complexes on the Thermostability of C-Reactive Protein (CRP), *Sci. Rep.* 11 (1) (2021) 13017.
[74] V. Leung, J. Mapletoft, A. Zhang, A. Lee, F. Vahedi, M. Chew, A. Szewczyk, S. Jahanshahi-Anbuhi, J. Ang, B. Cowbrough, M.S. Miller, A. Ashkar, C.D.M. Filipe, Thermal Stabilization of Viral Vaccines in Low-Cost Sugar Films, Sci Rep 9 (1) (2019) 7631.

[75] Y. Huo, X. Hou, Y. Yu, X. Wen, Y. Ding, Y. Li, Z. Wang, Improving the Thermal and Oxidative Stability of Food-Grade Phycocyanin from Arthrospira Platensis by Addition of Saccharides and Sugar Alcohols, Foods 11 (12) (2022) 1752.

[76] Y. Liang, L. Matia-Merino, H. Patel, A. Ye, G. Gillies, M. Golding, Effect of Sugar Type and Concentration on the Heat Coagulation of Oil-in-Water Emulsions Stabilized by Milk-Protein-Concentrate, Food Hydrocolloids 41 (2014) 332-342.

[77] S. Ramukutty, E. Ramachandran, Reaction Rate Models for the Thermal Decomposition of Ibuprofen Crystals, Journal of Crystallization Process and Technology 4 (2014) 71-78.

[78] R. Arjmandi, A. Hassan, M.K.M. Haafiz, Z. Zakaria, Md. S. Islam, Effect of Hydrolysed Cellulose Nanowhiskers on Properties of Montmorillonite/Polylactic Acid Nanocomposites, International Journal of Biological Macromolecules 82 (2016) 998-1010.

[79] D. Trache, Comments on "Thermal Degradation Behavior of Hypochlorite-Oxidized Starch Nanocrystals under Different Oxidized Levels, Carbohydrate Polymers 151 (2016) 535-537.

[80] M.A. Farrukh, K.M. Butt, K.-K. Chong, W.S. Chang, Photoluminescence Emission Behavior on the Reduced Band Gap of Fe Doping in CeO2-SiO2 Nanocomposite and Photophysical Properties, Journal of Saudi Chemical Society 23 (5) (2019) 561-575.

[81] A.G. Rusu, M.I. Popa, G. Lisa, L. Vereziuc, Thermal Behavior of Hydrophobically Modified Hydrogels Using TGA/FTIR/MS Analysis Technique, Thermochimica Acta 613 (2015) 28-40.

[82] B. Janković, B. Adnadević, J. Jovanović, Application of Model-Fitting and Model-Free Kinetics to the Study of Non-Isothermal Dehydration of Equilibrium Swollen Poly (Acrylic Acid) Hydrogel: Thermogravimetric Analysis, Thermochimica Acta 457 (2) (2007) 106-115.

[83] F.B. Santos, N.T. Miranda, M.I.R.B. Schiavon, L.V. Fregolente, M.R. Wolf Maciel, Thermal Degradation Kinetic of Poly(Acrylamide-Co-Sodium Acrylate) Hydrogel Applying Isoconversional Methods, J Therm Anal Calorim 146 (6) (2021) 2503-2514.

[84] M.T. Kalichevsky, J.M.V. Blanshard, P.F. Tokargzuk, Effect of Water Content and Sugars on the Glass Transition of Casein and Sodium Caseinate, Int J of Food Sci Tech 28 (2) (1993) 139-151.

[85] H. Kumagai, W. MacNaughtan, I.A. Farhat, J.R. Mitchell, The Influence of Carrageenan on Molecular Mobility in Low Moisture Amorphous Sugars, Carbohydrate Polymers 48 (4) (2002) 341-349.

[86] F.A. Momany, J.L. Willett, Molecular Dynamics Calculations on Amylose Fragments. I. Glass Transition Temperatures of Maltodecaose at 1, 5, 10, and 15.8% Hydration, Biopolymers 63 (2) (2002) 99-110.

[87] S. Kasapis, Recent Advances and Future Challenges in the Explanation and Exploitation of the Network Glass Transition of High Sugar/Biopolymer Mixtures, Critical Reviews in Food Science and Nutrition 48 (2) (2008) 185-203.