Synthesis and characterization of partially biodegradable and thermosensitive hydrogel

A partially biodegradable and thermosensitive hybrid hydrogel network (DAN series) based on dextran-allylisocyanate (Dex-Al) and poly(N-isopropylacrylamide) (PNIPAAm) was synthesized via UV photocrosslinking. These hybrid hydrogels were characterized in terms of their chemical structure, thermal, mechanical, morphological and temperature-induced swelling properties. The effect of the composition ratio of Dex-Al to PNIPAAm on such properties were examined. The differential scanning calorimetry data show that this Dex-Al/ PNIPAAm hybrid network has an increased lower critical solution temperature (LCST) and glass transition temperature (T-g) with an increase in the Dex-Al content. The interior morphology of these hybrid hydrogels revealed a decreased porous microstructure with an increase in the Dex-Al content in the hybrid network. Furthermore, if the Dex-Al composition became too high, a distinctive network structure with two different microporous structures appeared. The mechanical properties of these hybrid hydrogels also increased with an increase in the Dex-Al content. The temperature dependence of the swelling ratio, the deswelling kinetics as well as the reswelling kinetics was also characterized by gravimetric method. When comparing with a normal PNIPAAm hydrogel, these Dex-Al/PNIPAAm hybrid networks, due to the presence of Dex-Al moiety, also show improved temperature-induced intelligent properties, such as the faster and controllable response dynamics, which may find promising applications in a wide variety of fields, such as biomedical and bioengineering fields. (C) 2004 Kluwer Academic Publishers.