Investigation of the swelling behavior of hydrogels derived from high molecular weight Poly(2-Ethyl-2-Oxazoline)

Abstract

Thermoresponsive hydrogels are of great importance as smart materials. They are usually composed of cross‐linked polymers with a lower critical solution temperature (LCST). Although much is known about networks of poly(N‐isopropylacrylamide), all other polymers are somewhat neglected. In this work, the temperature‐dependent swelling behavior of differently cross‐linked thermoresponsive poly(2‐ethyl‐2‐oxazoline) (PEtOx) hydrogels were investigated with regard to varying parameters of the network composition. It was found that the degrees of swelling of the hydrogels converge for a certain polymer/solvent system at a distinct temperature independent of its degree of cross‐linking. Furthermore, this temperature correlates with the LCST of the respective starting PEtOx. Its net chain molecular weight Mc only affects the maximum degree of swelling and thus, the swelling–deswelling rate of the hydrogel. The fundamental structure/property relations found in this study could be useful to predict the behavior of other thermoresponsive hydrogels.