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ArticleVisualization of Polymer Chain Scission during Melt Processing
Using a Mechanochromic Probe
Wichean Khawdas, Yuto Kubota, Takumi Yamamoto, Hideyuki Otsuka, and Hiroshi Ito*
Cite This: https://doi.org/10.1021/acs.macromol.3c02182

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ABSTRACT: We thoroughly investigated polymer chain scission occurring
through thermal and mechanical degradation during kneading via complex
viscosity, torque, shear stress, and feeding rate measurements. We visualized
polystyrene chain scission using a diarylacetonitrile derivative (DAAN−
triOMe/triOMe) that can react with mechanoradicals to generate thecorresponding fluorescent DAAN−triOMe/triOMe radicals. We kneaded
polystyrene containing 5 wt % DAAN−triOMe/triOMe at various screw
speeds and kneading temperatures using a twin-screw kneader. The results
reveal that changes in complex viscosity and fluorescence intensity arecorrelated, indicating polystyrene chain scission and free radical generation.
Mechanochromic behavior was also associated with heat-induced polymer
deformation. Furthermore, the complex viscosity decreased with increasing speed and temperature. The analyses of torque, shear
stress, and feeding rate revealed intricate relationships between speed, temperature, and polymer chain scission. This study highlights
the effectiveness of DAAN−triOMe/triOMe in visualizing polymer chain scission using color change during both at-line and offline
observations.
measuring equipment.8−12 Mechanochromic materials play a
crucial role in process monitoring and control by enabling realtime visual observation of stress concentrations, enabling
operators to adjust processing parameters promptly for
improved efficiency and quality. They aid in processoptimization by identifying stress and strain areas during
extrusion, allowing engineers to adjust processing parameterssuch as temperature and pressure to achieve a more controlled
process. In quality assurance, these materials detect defects
early, reducing waste and ensuring product consistency
through uniform color changes across molded parts. Notably,mechanochromic polymers exhibit color change in response tomechanical stimulation and hold significant promise fordetecting material damage and stress,13 allowing timely
replacements or repair.
The present study investigated the impact of screw
rotational speeds, kneading temperatures, and feeding rates
on the generation of mechanoradicals in polystyrene (PS)blended with a diarylacetonitrile derivative (DAAN−triOMe/
triOMe). In particular, fluorescence intensity, shear stress, andcomplex viscosity measurements were used to explore polymer

1. INTRODUCTION
Screw extrusion is the commonly used technique for melting
commercial thermoplastic polymers and compounding additives or modifiers in the plastic manufacturing industry. The
polymers are melted through the combined heat generated by
the heater bands and shear heating created by the friction
between the granules and the screw and barrel. However, thehigh shear and heat to which the polymer is exposed during
extrusion cause thermomechanical degradation.1,2 Melt processing causes considerable polymer degradation, resulting insignificant changes in molecular weight, rheological properties,
crystallization behavior, and yellowness, which affects themechanical properties.3 Polymer processing causes degradation, as evidenced by changes in molecular weight stemmingfrom exposure to elevated temperatures, shear forces, andmechanical stress. Thermal and mechanical stresses generally
cause irreversible damage to the material within the extruder.
Such damage is caused through thermal, thermal-oxidative,
thermal-mechanical, or hydrolytic degradation mechanisms.4−7
Understanding polymer mechanical behavior and flow
dynamics during deformation and melt processing isimperative for optimizing performance and processing
parameters.
During these processes, stress visualization techniques
provide invaluable insights into stress distribution patterns
within polymers. Mechanochromic materials undergo reversible color changes in response to mechanical stress and thus
may be used for real-time stress visualization, enabling theanalysis of stress distribution in polymers without external© XXXX American Chemical Society

Received: October 25, 2023
Revised: June 9, 2024
Accepted: June 28, 2024A

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ArticleScheme 1. Extrusion Process Illustrating the Visualization of Polymer Chain Scission Mechanisms using Mechanochromic
Materials

2.3.3. Shear Stress. Shear stress measurements were performed
using a capillary rheometer (Toyo Seiki Seisakusho, Ltd., Tokyo,
Japan, CAPILOGRAPH1D) with the following specifications: barrel
diameter 9.5 mm, extrusion die diameter 1.0 mm, extrusion die length
40 mm (L/D = 40), and an operating temperature range of 150−180°C.

chain scission and mechanoradical generation. At-line observation of the polymer chain scission can be achieved bymonitoring the color change of the extrudate during the
extrusion process (Scheme 1). However, rheological, physicalthermal, and mechanical properties cannot be fully assessed
through the state of molten polymer. Consequently, theextrudates are prepared via compression molding as offline
samples for a more comprehensive analysis. The relationshipbetween color change and chain scission in these offline
samples could provide insights into the properties relevant toin situ or at-line observation.

3. RESULTS AND DISCUSSION
3.1. Optimization of DAAN−triOMe/triOMe Quantity
and Kneading Temperature Range. Thermal degradation
can cause polymer chain scission.5,13 Therefore, optimizing thekneading temperature using a twin-screw kneading extruder
was considered crucial for preventing the degradation of PS
while adjusting other kneading parameters. DAAN−triOMe/
triOMe was kneaded with PS to observe polymer chain
scission. Samples obtained at different kneading temperatures,ranging from 150 to 240 °C,15 were compression-molded.
Subsequently, the compressed samples were analyzed for
fluorescence intensity, and the complex viscosity of thecompressed samples was determined. Fluorescence emission
was chosen for measuring the changes in mechanochromic
polymers because of its sensitivity to mechanical stress,
noninvasive nature, real-time monitoring potential, and ability
to provide quantitative insights into stress-inducedchanges.10,12 Viscosity is associated with the molecular weight
and fluidity of the polymer.16−18 The fluorescence intensity of
DAAN−triOMe/triOMe was examined at different concentrations: 1, 3, and 5 wt %. These tests were conducted under
the following processing conditions: a kneading temperature of
180 °C, screw speed of 50 rpm, and duration of 3 min. Basedon the results presented in Figure 1a, a DAAN−triOMe/
triOMe concentration of 5 wt % was selected for all subsequent
experiments. Importantly, no fluorescence was observed forneat PS. The PS with 5 wt % DAAN−triOMe/triOMe wassubsequently kneaded at various temperatures.
The effect of heat on polymers is well-established, as it cansignificantly impact their behavior and properties. With
increasing temperature, the thermal energy of the polymers
increases,13 which can lead to polymer chain scission or
decomposition.3,5,7 At considerably high temperatures, polymer molecules absorb sufficient thermal energy to break

2. MATERIALS AND METHODS
2.1. Materials. Commercial-grade PS, designated grade 679 (Mw∼ 255,123, Mn ∼ 107,653, and MWD ∼ 2.37), was procured from PSJ
Japan Co., Ltd. The mechanochromic probe material, DAAN−
triOMe/triOMe, was synthesized according to a previously reported
method.14 All materials were used without additional purification.
2.2. Experimental Procedures. 2.2.1. Kneading Process. PS
with DAAN−triOMe/triOMe was kneaded in a twin-screw kneading
extruder (LABO PLASTOMILL 4C150, Toyo Seiki Seisakusho, Ltd.,Tokyo, Japan) at different temperatures, screw rotational speeds,
torques, and feeding rates.
2.2.2. Compression Molding. Compression molding was performed using a vacuum melting heat press (Imoto Machinery Co.,
Ltd., IMC-11FA). The compressed samples for complex viscosity andfluorescence intensity measurements were prepared as follows: thethickness of the sample was 1 mm, preheated at 140 °C for 5 min,applying a pressure of 4 MPa for 5 min and cooling at 15 °C for 5
min. The experimental procedure of visualization and characterizationof polymer chain scission is shown in Figure S1 (Supplementarydata).
2.3. Characterization. 2.3.1. Complex Viscosity. Rheologicalproperties of the melt were assessed using a modular compact
rheometer 302 (Anton Paar Japan K.K., Tokyo, Japan) equipped with
8 mm in diameter parallel plates. The samples were measured under a
10% strain within the frequency range of 0.1−100 rad s−1 at aconstant temperature of 210 °C for approximately 30 min (which isthe entire measurement duration) under a N2 atmosphere.
2.3.2. Fluorescence Intensity. Fluorescence intensity was quantified using a spectrofluorometer (Japan Spectroscopy (JASCO) Co.,
Ltd., FP-8550VSR) across a wavelength range of 500−800 nm.
B

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Articlefor the exploration of other parameters that could contribute topolymer chain scission.
Based on a previous study, electron paramagnetic resonance(EPR) was employed to identify polymeric mechanoradical
generated through polymer scission, facilitating a quantitative
assessment of DAAN species. Notably, fluorescence became
evident postgrinding. EPR measurements distinctly illustrated
a signal corresponding to the formation of radical species,aligning with EPR spectra. Additionally, the fluorescence
spectrum exhibited an increase in fluorescence intensity withDAAN radical quantity over grinding time. A direct correlation
between fluorescence intensity and DAAN radical amount wasestablished.20 The color change and chemical mechanism areillustrated in Scheme 1.
3.2. Mechanochromic Behavior at Different Screw
Speeds and Kneading Temperatures. As previously
mentioned, heat affects polymer chain scission. However,kneading temperatures in the range of 150−180 °C areconsidered suitable for PS. To gain further insights, the PS
kneading temperatures of 150, 160, 170, and 180 °C were
investigated. The rotational speed of the screw in polymer
processing, particularly in extrusion and kneading, plays asignificant role in polymer chain scission.2,3,15,21 The screw
speed determines how quickly the polymer material istransported through the processing equipment and can havea notable impact on polymer properties as a result of shear
forces, heat generation, and processing time.22,23 To address
this, screw speeds ranging from 10 to 200 rpm were
investigated to elucidate polymer chain scission mechanisms.
For each kneading condition, the torque and temperature of
the melt polymer were simultaneously recorded (Figure 4).
DAAN−triOMe/triOMe exhibits mechanochromic behavior
when polymeric mechanoradicals abstract hydrogen radical
from DAAN−triOMe/triOMe14,20 and generate the corre-

Figure 1. (a) Fluorescence emission spectra (λex = 365 nm) of
DAAN−triOMe/triOMe/PS at 1, 3, and 5 wt % of DAAN−triOMe/
triOMe, and (b) complex viscosity of DAAN−triOMe/triOMe/PS asa function of angular frequency measured at 210 °C from the kneaded
samples at various kneading temperatures and a screw speed of 50rpm. * = Samples prepared by compression molding at 140 °C.

certain chemical bonds within them and generate free radicals.
Consequently, the application of heat to the polymer leads toan increase in the generation of free radicals.7,13 The effects ofsuch thermally induced changes are manifold, encompassing
alterations in molecular weight, weight distribution, and degreeof crystallinity. Notably, the complex viscosity of PS decreases
at kneading temperatures of 210 and 240 °C, indicating a
reduction in molecular weight due to the thermal degradationof the polymer chain at relatively high temperatures.5,19 The
results indicated an optimal kneading temperature range of150−180 °C. This range was selected due to its ability tomaintain a complex viscosity value closely preserving that ofneat PS. Furthermore, as depicted in Figure 4, temperatures
exceeding 180 °C at a screw rotational speed of above 150 rpm
result in the polymer melt temperature reaching approximately
200 °C, potentially leading to thermal degradation. This
kneading temperature range (150−180 °C) with 5 wt %DAAN−triOMe/triOMe provides a suitable reference point

Figure 2. (a) Fluorescence emission spectra (λex = 365 nm) of DAAN−triOMe/triOMe/PS and the neat PS at a constant screw speed of 50 rpm atvarious kneading temperatures, with (b) corresponding photographs. (c) Fluorescence emission spectra (λex = 365 nm) of DAAN−triOMe/
triOMe/PS and the neat PS at different screw rotation speeds at 150 °C and, with (d) corresponding photographs. * = Samples prepared bycompression molding at 140 °C. (All photographs were acquired under fluorescence conditions at an excitation wavelength of 365 nm.)C

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ArticleFigure 3. (a) Complex viscosity of DAAN−triOMe/triOMe/PS measured at 210 °C from the samples kneaded at a constant kneading temperatureof 150 °C at different kneading screw rotational speeds, and (b) complex viscosity of neat PS and DAAN−triOMe/triOMe/PS at a constant screw
speed of 50 rpm at different kneading temperatures. * = Samples prepared by compression molding at 140 °C.

sponding DAAN−triOMe/triOMe radical that emits orange
fluorescence with a band around 580 nm. As shown in Figure
2a, b, the fluorescence intensity sequentially increases as thetemperature decreases from 180 to 150 °C. This suggests thatthe chain scission of PS at 180 °C is less pronounced than thatat 150 °C. The compression process followed for fluorescenceand complex viscosity measurements was assumed to notfurther induce color change at 140 °C as previous study.11
Thermogravimetric analysis showed that the degradation
temperature of DAAN was quite high at approximately 240°C, indicating high thermal stability (Figure S2). Furthermore,as shown in Figure 2b, d, the kneaded and compressed samples
showed similar colors. Similarly, as shown in Figure 3b, thecomplex viscosity at 180 °C is higher than that at 150 °C,
indicating a higher molecular weight and less pronounced
polymer chain scission. Consequently, reduced fluorescenceintensity is observed.
In contrast, fluorescence intensity increases with the screw
rotational speed. In particular, at a screw speed of 200 rpm, thefluorescence intensity is 25% higher than at 10 rpm (the lowest
speed). Figure 2c, d illustrates that the orange fluorescence
becomes more pronounced at higher screw rotational speeds.
These elevated speeds, in conjunction with higher temperatures, are believed to enhance the generation of PS radicals.
The increased breakage of polymer chains, attributed to higher
screw rotational speeds and the associated higher loads,23 leads
to greater generation of DAAN−triOMe/triOMe radicals
owing to the hydrogen atom transfer reaction by the PS
radicals generated during kneading.20 Consequently, higher
fluorescence intensity is observed at higher screw rotational
speeds compared with lower rates. The observed variations influorescence intensity with screw rotational speeds andkneading temperatures suggest a close relationship between
polymer chain scission, i.e., mechanoradical generation, andthe fluorescence behavior of DAAN−triOMe/triOMe radicals.
3.3. Complex Viscosity at Different Screw Speeds andKneading Temperatures. Rheological assessment of melted
polymers has proven to be one of the most efficient techniques
for indirectly assessing degradation changes in thermoplastic
polymer materials during processing.16 The viscosity ofpolymers is directly linked to their molecular weight, withhigher-molecular-weight polymers exhibiting greater viscosity
than their lower-molecular-weight counterparts.18,19 Thus,
complex viscosity measurements were employed to investigate
polymer chain scission depending on molecular weight atvarious kneading temperatures.

Figure 3a presents a comparison of screw rotational speeds
and their impact on complex viscosity, storage modulus, andloss modulus. It is evident that as the screw rotational speed
increases, the melt viscosity decreases. This observation
indicates that higher screw rotational speeds promote thepolymer chain scission.24 As is widely recognized, shear forces
and mechanical stresses22 exerted on polymer chains at higher
rotational speeds facilitate the rupture of molecular bonds,
leading to a reduction in viscosity. Consequently, the polymer
is degraded, resulting in an overall decrease in its viscosity.
Figure 3b illustrates the effect of different kneading
temperatures on melt viscosity. Samples kneaded at low
temperatures exhibit lower viscosity than those processed at
higher temperatures. The higher the kneading temperature, thegreater the fluidity of the polymer resin.25 This phenomenon
can be attributed to the increased mobility of polymer chains at
higher temperatures, resulting in a decrease in shear forces.
Consequently, the cleavage of molecular chains is hindered,preserving the overall molecular integrity of the polymer and,
therefore, leading to a higher melt viscosity.19 Due to polymer
chain scission, the use of higher screw speeds or lower
kneading temperatures could induce a decrease in G′ and G″
compared with neat PS. As a result, based on the findings, akneading temperature of 180 °C was considered optimal at 50rpm.
3.4. Torque as a Function of Screw Speed andTemperature. Torque measurements were used to investigate
the reasons behind the reduced fluorescence intensity and highviscosity at higher temperatures (Figure 2). Torque measurement is a sensitive method for comparative and quantitative
assessments of melt viscosity, molar mass, mechanical force,and stress to polymers in real-time during melt processing,particularly for detecting incipient degradation.26 The relationship between torque and polymer chain scission involves themechanical forces generated by screw rotation, which can
induce the degradation of polymer materials. Torque wasapplied to study some insight into melting behavior due topolymer chain scission.27 The mechanical stress from screw
rotation can cleave chemical bonds within polymer chains,resulting in the formation of smaller fragments, altering themelt properties. This relationship is significant in applications
where mechanical stress is applied to polymers.
In this study, the software embedded within the kneadingmachine simultaneously recorded both torque values and thetemperature change of the melt polymer throughout eachkneading process of the PS melt from the previouslyDhttps://doi.org/10.1021/acs.macromol.3c02182
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mentioned experiment 3.2 under varying screw rotational
speeds (at 150 °C) and kneading temperatures (at 50 rpm). As
shown in Figure 4a, the torque is initially higher at higher

Articletemperature of the PS melt changes to approximately 4, 2, 1,
and 0 °C, respectively. This indicates that higher screw speeds
and lower kneading temperatures induce more heat generation
due to higher shear rates. The toque values (Figure 4b) andthe kneading temperature at 180 °C (Figure 4d) were constantindicating no heat generated reflexing less shear stress thanthose of lower kneading temperatures.
However, at lower screw rotational speeds�indicative of
reduced load applied on the PS�the torque decreases withincreasing kneading temperature. This observation aligns with
the increased fluidity of the resin at higher kneading
temperatures, leading to a decreased load on the resin.
Consequently, it is presumed that polymer chain scission is lesslikely, consistent with the trends observed in Figures 2a and3b.
Elevated torque within the kneading extruder can generatehigh shear stress on the polymer melt, increasing the likelihoodof polymer chain scission, particularly for polymers sensitive toshear-induced degradation. Excessive torque and shear stresscan induce chain scission, thereby reducing the molecularweight of the polymer and potentially affecting its properties.22
3.5. Relationship between Shear stress and Fluorescence Intensity. Elevated torque in the extruder increases
the shear force and stress on the polymer melt. Thus, we
elucidated the relationship between shear stress andfluorescence intensity. Shear stress was computed using
Equation 1, and the average shear rate, as given in Eq (4),Figure 4. Torque recorded during the kneading process as a functionof kneading time over 3 min at different (a) screw rotational speedsand (b) kneading temperatures. (c, d) Temperature of the PS melt.

screw rotational speeds. However, it gradually decreases as
kneading progresses. This behavior was attributed to theincreased load and subsequent heat generation associated withincreased screw rotational speeds, as shown in Figure 4c.
Under such conditions, PS experiences greater stress at higher
screw rotational speeds than that at lower screw rotational
speeds,28 increasing the likelihood of polymer chain scission.
Furthermore, the temperature of the PS melt increases as thescrew rotational speed increases. The increase of the melt
polymer temperature at 10, 50, 100, 150, and 200 rpm isapproximately 0, 4, 11, 17, and 22 °C, respectively. At different
kneading temperatures of 150, 160, 170, and 180 °C, theFigure 5. Shear stress and fluorescence intensity at different (a) screw speeds and (b) kneading temperatures; (c) relationship between
fluorescence intensity and shear stress. * = Samples prepared by compression molding at 140 °C.
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ArticleFigure 6. (a) Fluorescence intensity and (b) complex viscosity and of DAAN−triOMe/triOMe/PS measured at 210 °C from the samples kneaded
at a constant screw rotational speed of 100 rpm and different feeding rates. * = Samples prepared by compression molding at 140 °C.

was initially derived from Eqs (2) and (3) based on the screw
type, as illustrated below:
Here, τ is the shear stress, η is shear viscosity, γ̇ is the shear
rate, D is the inner diameter of the cylinder, N is the screw
rotational speed, Ct0 is the minimum tip clearance, and Ctθ isthe minimum tip clearance at any angle.29
The effects of rotational speeds and their impact on shear
rate were investigated at a kneading temperature of 150 °C.
The results show that at a screw rotational speed of 10 rpm(γ̇min), the shear stress is approximately 1.6 × 105 Pa.
Conversely, at 200 rpm, it increases to approximately 1.3 ×
106 Pa (γ̇max), as demonstrated in Figure S3a. The determined
shear rate and shear stress at various kneading temperatures
but constant screw rotational speed of 50 rpm are given in
Figure S3b. The obtained shear stress values at 150 and 180 °C
are approximately 5.6 × 105 and 1.0 × 105 Pa, respectively.
These findings underscore the significance of the effects ofboth screw rotational speed and kneading temperature on theshear rate and resin viscosity during kneading.
Figure 5c shows a notable correlation between shear stressand fluorescence intensity. This implies that the application ofshear stress to the PS results in a discernible change in its
fluorescence intensity. DAAN−triOMe/triOMe radicals in the
PS matrix emit fluorescence in response to mechanical stress.
Consequently, an increase in shear stress leads to acorresponding change in the fluorescence intensity of the PS.
With increasing applied shear stress, molecular chains of PS
undergo cutting or scission. This indicates that higher shear
stress causes mechanical deformation of the PS, leading to thebreakage of the molecular chains.30 The correlation between
shear stress and fluorescence intensity can also aid theunderstanding of mechanical scission and molecular changes.
3.6. Relationship between Feeding Rates andFluorescence Intensity. The negative correlation between
feeding rate and residence time within an extruder is significant
in polymer processing. A longer residence time may increase
the shear and thermal degradation of the polymer, ultimately
impacting material properties.
Figure 6 shows the effect of feeding rate on the duration ofshear and heating during the processing of the material in thekneading extruder. At lower feeding rates, shear is applied foran extended period, leading to molecular chain scission.
Conversely, with increasing feeding rate, as shown in Figure
S4a, the polymer experiences shear for a shorter time, reducing
the likelihood of molecular chain scission.31,32 Consequently,
Figure 6b exhibits a relatively higher fluorescence intensity atlower feeding rates, coinciding with the lower complex
viscosity in Figure 6a. The impact of the feeding rate on the
duration of shear plays a critical role in determining the extent

of molecular chain scission within the polymer during
kneading. These findings significantly contribute to theunderstanding of polymer scission behavior and have
implications for the optimization of kneading parameters toachieve desired material properties.

4. CONCLUSIONSThis study has explored relations among heat, mechanicalforces, and polymer chain scission using the mechanofluorescent probe in polymer processing. The effect of heat on
polymers became evident through observable alterations intheir properties and behavior at elevated temperatures. Hightemperatures induced increased fluidity, leading to either
polymer chain scission due to the cleavage of chemical bonds
and the generation of free radicals. Correlations between
fluorescence intensity and various parameters were clarified.
We found that higher screw rotational speeds enhanced
fluorescence intensity because of intensified polymer chain
breakage, as confirmed by a set of experimental data fromcomplex viscosity, torque, shear stress, and fluorescenceintensity measurements, all these results are related to eachother. In contrast, suitable kneading temperatures wereassociated with reduced fluorescence owing to nonradical
adduct formation. The mechanochromic behavior of DAAN−
triOMe/triOMe under the effects of heating and shear resulted
in the generation of mechanoradicals and fluorescenceemission, providing insights into the effect of mechanicalstress on polymer behavior. The relationship between shear
stress, shear rate, and polymer scission revealed that higher
shear stress corresponds to increased fluorescence intensity,reflecting polymer chain scission and deformation. Additionally, this study underscores the significance of residence time in
the kneading extruder, where longer residence times promote
the scission of molecular chains.
The insights obtained in this study are pivotal for optimizing
polymer processing conditions. They will guide the selection of
appropriate temperatures and shear rates, which are essential
for achieving desired material properties. Furthermore, thisstudy proposes a visual indicator of stress distribution andmolecular chain scission, offering researchers a valuable tool
for studying the mechanical behavior of polymers during
deformation and flow. Additionally, the findings of this study
contribute to the understanding of polymer chain scission,
which is crucial for the development of advanced materials.
Moreover, this study lays a strong foundation for further
exploration of polymer behavior under different processing
conditions. It facilitates advancements in the visualization ofpolymer scission and degradation, providing immense value inmaterial science and engineering.
F

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Its Nanogel Particles Controlled by Variable Pitch and Differential* Supporting Information
sı

The Supporting Information is available free of charge athttps://pubs.acs.org/doi/10.1021/acs.macromol.3c02182.
Experimental procedures of visualization and characterization of polymer chain scission; thermogravimetricanalysis (TGA) graph of DAAN degradation temperature; relationship of screw speeds and shear rates aswell as shear rates and shear stresses at different
temperatures; output volume of different feeding rates
at 100 rpm and different screw rotational speeds at aconstant feeding rate of 8.3 g/min, 3 min (PDF)■

AUTHOR INFORMATION

Corresponding Author

Hiroshi Ito − Research Center for GREEN Materials andAdvanced Processing, Yamagata University, Yonezawa,
Yamagata 992-8510, Japan; orcid.org/0000-0001-84328457; Email: ihiroshi@yz.yamagata-u.ac.jp
Authors

Wichean Khawdas − Research Center for GREEN Materials
and Advanced Processing, Yamagata University, Yonezawa,
Yamagata 992-8510, Japan; orcid.org/0009-0007-30653386
Yuto Kubota − Department of Organic Materials Science,
Graduate School of Organic Materials Science, Yamagata
University, Yonezawa, Yamagata 992-8510, Japan
Takumi Yamamoto − Department of Chemical Science andEngineering, Tokyo Institute of Technology, Meguro-ku,
Tokyo 152-8550, Japan; orcid.org/0009-0002-68450166
Hideyuki Otsuka − Department of Chemical Science andEngineering, Tokyo Institute of Technology, Meguro-ku,
Tokyo 152-8550, Japan; orcid.org/0000-0002-1512671X
Complete contact information is available at:https://pubs.acs.org/10.1021/acs.macromol.3c02182
Notes

The authors declare no competing financial interest.

■■■

ArticleACKNOWLEDGMENTS

This work was financially supported by JST CREST Grant
JPMJCR1991 (Japan).

ABBREVIATIONS
PS, polystyrene; DAAN−triOMe/triOMe, diarylacetonitrile
derivative with six methoxy groups
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