Studies on preparation and swelling properties of the N‐isopropylacrylamide/chitosan semi‐IPN and IPN hydrogels

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Abstract
Semi‐interpenetrating network (semi‐IPN) polymer gels and interpenetrating network (IPN) polymer gels with thermosensitivity were prepared by introducing a biodegradable polymer, chitosan, into the N‐isopropyacrylamide (PNIPAAm) gel system. The swelling behavior, temperature sensitivity, pH sensitivity, gel strength, and drug‐release behavior of PNIPAAm/chitosan semi‐IPN and IPN hydrogels were investigated. The results indicated that the NIPAAm/chitosan semi‐IPN and IPN hydrogels exhibited pH and temperature‐sensitivity behavior and could slow drug release and diffusion from the gels. From the stress–strain curves of the hydrogels, the compression moduli of IPN gels containing crosslinked chitosan were higher than those of semi‐IPN gels. This is because IPN gels have a more compact structure. The morphology of PNIPAAm/chitosan hydrogels was also investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2487–2496, 2001