Stimuli-Responsive Hydrogels Based on Random Copolymers of the Sucrose Methacrylate

Poly(sucrose methacrylate-co-acrylic acid), P(SMA-co-AA), and poly(sucrose methacrylate-co-diethylene glycol methyl ether methacrylate), P(SMA-co-EG(2)MA), are synthesized by free radical polymerization using sucrose dimethacrylate as a crosslinker. The copolymers present one glass transition suggesting a random distribution of the comonomers. The copolymers-water interaction parameter chi is around 0.5, while M-c increases with SMA molar fraction. The kinetics of water swelling show a Fickian behavior for P(SMA-co-AA) richer in acrylic acid. The swelling is driven by the ionic character of the P(SMA-co-AA), except at pH = 2, and by the hydrophilicity of the SMA for the P(SMA-co-EG(2)MA). The temperature influences the swelling behavior of the P(SMA-co-EG(2)MA) due to the lower critical solution temperature (LCST) behavior. The pH- and thermoresponsiveness of the P(SMA-co-AA) and P(SMA-co-EG(2)MA) hydrogels are maintained by replacing the sensitive comonomers with SMA up to mass fractions of 85 and 20 wt%, respectively, approximate to 71 and 17 wt% of sucrose, a product from a renewable resource. The hydrolytic degradation of the hydrogels is more pronounced for copolymers richer in SMA and resulted in sucrose release. Hydrogels present viscoelastic behavior, and the P(SMA-co-AA) series is more resistant to compression. The xerogels of the copolymers richer in SMA show a foam-like morphology with open cells.