Comparison of Thermoresponsive Deswelling Kinetics of Poly(oligo(ethylene oxide) methacrylate)-Based Thermoresponsive Hydrogels Prepared by “Graft-from” ATRP

Cross-linked thermoresponsive poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene oxide) methyl ether methacrylate-co-2-hydroxyethyl methacrylate-co-ethylene glycol dimethacrylate) hydrogels (poly(MEO2MA−OEOMA−HEMA hydrogels) were prepared by atom transfer radical polymerization (ATRP). The hydroxyl groups in the formed gel networks were transformed to ATRP initiating sites containing 2-bromoisobutyrate groups, and the modified gels were used as macroinitiators for “graft-from” ATRP of MEO2MA and OEOMA. The thermoresponsive properties of the resulting comb-type grafted hydrogels were compared to their unmodified precursor hydrogels with respect to the transition temperatures and deswelling rates. The thermoresponsive properties could be customized by changing the grafting density, grafted chain length, and the chain composition. Furthermore, the deswelling kinetics of the prepared hydrogels were quantitatively analyzed by exponential fitting of water retention with time. This analysis demonstrated that the grafted chains accelerated the hydrogel deswelling by providing a faster collapse to the globular structures, as assessed by much shorter water retention times for the grafted gels (