Raman spectroscopy study on influence of network architecture on hydration of poly(2-(2-methoxyethoxy) ethyl methacrylate) hydrogels

Thermo-responsive polymer hydrogels attract a great attention because of their unique behavior in response to changes in the thermal environment. It is related to metastable intermolecular interactions resulting in volume phase transitions (VPT). The hydration of poly(2-(2-methoxyethoxy) ethyl methacrylate) (PMEO(2)MA)-based materials was studied by Raman spectroscopy and further supported by density functional theory calculations. Hydrogels based on random networks prepared via radiationinduced free radical polymerization and cross-linking were compared with hydrogels withmore regular structure formed by atom transfer radical polymerization. Two types of regular networks were studied: bare one and decorated by linear dangling chains. It was found that both, the total bound water surrounding the polymer chains (similar to 11 H2O per polymer unit) and accessibility of C=O groups for water molecules, are independent of topology of PMEO2MA network. Contrarily, network architecture strongly influences C=O-water complex stability, which decreases in a following order: regular bare network, irregular bare network, regular decorated network. It was also shown that the stability of C=O-water complex is correlated with VPT temperature in PMEO2MA hydrogels. These studies prove a key role of polymer hydration in its thermo-responsive properties. Copyright (c) 2016 JohnWiley & Sons, Ltd.