Semi‐Interpenetrating Hydrogel Networks of Poly(2‐hydroxyethyl methacrylate) with Poly[(D,L‐lactic acid)‐co‐(ε‐caprolactam)]

Semi‐interpenetrating hydrogel networks (IPNs) composed of poly(2‐hydroxyethyl methacrylate), PHEMA, and poly(D ,L ‐lactic acid)‐co‐(ε‐caprolactam)], copoly(D,L ‐LA/ε‐CLM), were synthesized. Linear copoly(D,L ‐LA/ε‐CLM) chains were interpenetrated into the crosslinked three‐dimensional networks of PHEMA. Physical properties of IPN samples such as stress‐strain behavior, swelling, extraction and glass transition (T_g) were examined. Glass transition temperature of the PHEMA was shifted to lower temperatures, indicating interpenetration of PHEMA and copoly(D,L ‐LA/ε‐CLM) chains. The extraction results showed that the entrapping level between two components of PHEMA/copoly(D,L ‐LA/ε‐CLM) in simultaneous semi‐IPN is very high. These results confirm that the decrease in swelling ratios with increase in copoly(D,L ‐LA/ε‐CLM) contents is probably due to the entanglement effect. Semi‐IPNs showed higher ultimate strength and modulus but lower elongation with respect to pure PHEMA hydrogel. The semi‐IPN samples exhibited brittle fracture morphology which is consistent with tensile properties.