Influence of the grafted chain length on responsive behaviors of the grafted poly(DEA-co-DMAEMA) hydrogel

The poly(N,N-diethylacrylamide-co-(2-dimethylamino)ethyl methacrylate) (poly(DEA-co-DMAEMA)) macromonomers with three different chain lengths were prepared by telomerization of DEA and DMAEMA monomers with different ratios of the chain transfer agent, 2-mercaptoethanol. The number-average weight of three macromonomers determined by gel permeation chromatography of the terminal hydroxyl groups was 8355, 10,516 and 15,953, respectively. The comb-type grafted poly(DEA-co-DMAEMA) hydrogels having the different lengths of the grafted chains were synthesized in the presence of crosslinker. Equilibrium and dynamic swelling/deswelling properties of the prepared hydrogels responding to temperature and pH were investigated. Compared to normal-type hydrogel, the comb-type grafted hydrogels exhibited excellent variational values in response to an alternation of the temperature and pH. Moreover, the grafted hydrogels showed quite fast reswelling and deswelling behaviors in response to simultaneous dual temperature and pH stimuli. This is because that the introduction of side chains with freely mobile ends in the comb-type grafted hydrogels made the mobility of the networks increased. The responsive rates of the grafted hydrogels were also controlled by modifying the length of the grafted chains. The dual thermo- and pH-sensitive comb-type grafted poly(DEA-co-DMAEMA) hydrogels in this study may find various potential applications.