Evolution of high-temperature molecular relaxations in poly(2-(2-methoxyethoxy)ethyl methacrylate) upon network formation

Copolymers of 2-(2-methoxyethoxy)ethyl methacrylate (poly(MEO(2)MA)) are regarded as bioinert replacements of poly(N-isopropylacrylamide) in some biomedical applications. Networks of poly(MEO(2)MA) of various architecture form thermo-responsive hydrogels. Here, we present dielectric and mechanical spectroscopy studies on segmental motions and network relaxation processes in linear poly(MEO(2)MA) and its networks - bare network and the network grafted with short poly(MEO(2)MA) chains. We show that the alpha process assigned to the segmental motions of poly(MEO(2)MA) is independent on the polymer topology and the glass transition temperature, T (g), associated with this process equals 235-236 K for all investigated systems. The alpha' relaxation observed above T (g) by dynamical mechanical analysis is assigned to the sub-Rouse process. It strongly depends on the polymer network architecture and slows down by four orders of magnitude upon network formation.