Dynamic relaxation characteristics of crosslinked poly(ethylene oxide) copolymer networks: influence of short chain pendant groups

The dynamic relaxation characteristics of short-branch rubbery amorphous networks prepared by the photopolymerization of poly(ethylene glycol) diacrylate [PEGDA] crosslinker have been investigated using dynamic mechanical analysis and broadband dielectric spectroscopy. Copolymerization with low molecular weight acrylates was used to control effective crosslink density in the networks and led to the insertion of ethylene oxide pendant groups along the network backbone. Substantial differences in the sub-glass and glass-rubber relaxation properties of the copolymers were observed as a function of pendant length and the nature of the pendant terminal group (e.g., -OH vs. -OCH₃); the results are compared with prior studies on model copolymers containing longer, more flexible side branches.