Temperature-sensitive swelling behavior of polymer gel composed of poly (N,N-dimethylaminoethyl methacrylate) and its copolymers

Polymer gels composed of N,N-dimethylaminoethyl methacrylate (DMAEMA) and acrylamide (AAm) (or ethyl acrylamide (EAAm)) were prepared to observe temperature-sensitive swelling behavior. The temperature dependence of equilibrium swelling of poly (DMAEMA-co-AAm) gel was in accordance with the change of the lower critical solution temperature (LCST) of poly (DMAEMA-co-AAm) aqueous solution as a function of chemical composition. However, poly (DMAEMA-co-EAAm) gel did not show the similar trend to poly (DMAEMA-co-AAm) gel. In the case of poly (DMAEMA-co-AAm), the hydrogen bond, which played an important role in controlling the LCST, was maintained with the formation of the gel network. However, the hydrogen bond in poly (DMAEMA-co-EAAm) was disrupted significantly with the formation of the gel network. This led to the difference in swelling behavior of polymer gels in response to temperature.