Thermal and pH Responses of Hydrogels Based on Chitosan-g-N-Alkyl-Substituted Polyacrylamide Copolymers
- 1Centro de Investigación en Alimentación y Desarrollo, Hermosillo 83304, Sonora, Mexico
- 2Faculty of Chemistry, Universidad de La Habana, La Habana 10400, Cuba
Abstract
Chitosan grafted with N-alkyl-substituted polyacrylamide yields dual-responsive materials sensitive to both pH and temperature. For instance, the phase transition of poly(N,N-diethylacrylamide) can be tuned by copolymerizing it with more hydrophilic units, such as N,N-dimethylacrylamide or N-ethylacrylamide. While hydrophilic and hydrophobic interactions between macromolecular segments drive this phase transition, the specific role of hydrogen bonding between chitosan and the polyacrylamide grafts is not fully understood yet. Clarifying how these interactions influence the volume phase transition is essential for predicting hydrogel behavior. Chitosan-g-poly(DEAm-co-DMAm) and chitosan-g-poly(DEAm-co-NEAm) hydrogels showed continuous volume phase transitions that broadened with increased content of hydrophilic units (DMAm or NEAm). The critical temperature (Tc) of chitosan-g-poly(DEAm-co-DMAm) hydrogels increased linearly with the content of DMAm, while chitosan-g-poly(DEAm-co-NEAm) hydrogels exhibited a downward deviation from the linear variation in Tc from 0 to 100 mol-% DEAm. Both hydrogels showed higher swelling in acidic conditions at temperatures below the Tc, with a marked reduction as pH turned basic. Above the Tc, the pH response was almost negligible. Evidence suggests that the formation of hydrophobic domains of N,N-diethylacrylamide units during heating could bring the N-alkyl polyacrylamide and the chitosan chains closer together. This promotes inter-chain hydrogen bonding, which favors the cooperative character of the transition.
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BibTeX
@article{cocahidalgo2026thermal,
title = {{Thermal and pH Responses of Hydrogels Based on Chitosan-g-N-Alkyl-Substituted Polyacrylamide Copolymers}},
author = {José Javier Coca-Hidalgo and Carlos Peniche-Covas and Jaime Lizardi-Mendoza and Waldo Manuel Argüelles-Monal},
journal = {Polymers},
year = {2026},
month = nov,
doi = {10.3390/polym18212787},
url = {https://www.mdpi.com/2073-4360/18/21/2787},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Thermal and pH Responses of Hydrogels Based on Chitosan-g-N-Alkyl-Substituted Polyacrylamide Copolymers
AU - José Javier Coca-Hidalgo
AU - Carlos Peniche-Covas
AU - Jaime Lizardi-Mendoza
AU - Waldo Manuel Argüelles-Monal
PY - 2026
DA - 2026/11/07
JO - Polymers
DO - 10.3390/polym18212787
UR - https://www.mdpi.com/2073-4360/18/21/2787
AB - Chitosan grafted with N-alkyl-substituted polyacrylamide yields dual-responsive materials sensitive to both pH and temperature. For instance, the phase transition of poly(N,N-diethylacrylamide) can be tuned by copolymerizing it with more hydrophilic units, such as N,N-dimethylacrylamide or N-ethylacrylamide. While hydrophilic and hydrophobic interactions between macromolecular segments drive this phase transition, the specific role of hydrogen bonding between chitosan and the polyacrylamide grafts is not fully understood yet. Clarifying how these interactions influence the volume phase transition is essential for predicting hydrogel behavior. Chitosan-g-poly(DEAm-co-DMAm) and chitosan-g-poly(DEAm-co-NEAm) hydrogels showed continuous volume phase transitions that broadened with increased content of hydrophilic units (DMAm or NEAm). The critical temperature (Tc) of chitosan-g-poly(DEAm-co-DMAm) hydrogels increased linearly with the content of DMAm, while chitosan-g-poly(DEAm-co-NEAm) hydrogels exhibited a downward deviation from the linear variation in Tc from 0 to 100 mol-% DEAm. Both hydrogels showed higher swelling in acidic conditions at temperatures below the Tc, with a marked reduction as pH turned basic. Above the Tc, the pH response was almost negligible. Evidence suggests that the formation of hydrophobic domains of N,N-diethylacrylamide units during heating could bring the N-alkyl polyacrylamide and the chitosan chains closer together. This promotes inter-chain hydrogen bonding, which favors the cooperative character of the transition.
SN - 2073-4360
ER -