Synthesis and characterization of temperature- and pH-sensitive hydrogels based on poly(2-ethyl-2-oxazoline) and poly(D,L-lactide)

A novel series of temperature- and pH-sensitive hydrogels based on. poly(2-ethyl-2-oxazoline) and three-arm poly(D,L-lactide) were synthesized via photocopoly-merization. For the creation of polymeric networks, two types of macromers terminated with methacrylate groups were prepared: poly(2-ethyl-2-oxazoline) dimethacrylate and three-arm poly(D,L-lactide) trimethacrylate. The chemical structures were analyzed with H-1 NMR and Fourier transform infrared techniques. The thermal behaviors, morphologies, and swelling properties were measured for the characterization of the polymeric networks. All the poly(2-ethyl-2-oxazoline)/three-arm poly(D,L-lactide)hydrogels provided high water retention capacity and exhibited reversible swelling-shrinking behavior in response to temperature and pH variations. The hydrogels with higher poly(2-ethyl-2-oxazoline) dimethacrylate contents were more effective in raising the swelling ratio and temperature and pH sensitivity. However, higher contents of three-arm poly(D,L-lactide) trimethacrylate produced larger particles and pore sizes in the hydrogels. This study effectively proves that this unique combination of water swellability and biodegradability provides hydrogels with a much wider range of applications in biomedical fields. (C) 2002 Wiley Periodicals, Inc.