Structural characterization of chitosan-grafted polyurethanes

Biohybrid polyurethane-grafted-chitosan hydrogels were synthesized by a heterogeneous synthetic method. Chitosan-grafted polyurethane hydrogels were prepared. Their analogous, without chitosan, were studied as control. Hydrogels were prepared using bis(cyclohexyl)methane-4,4’-diisocyanate, 1,4-butanediol, a crosslinking agent and, alternatively, polyethylene-oxide or polyethylene-adipate as macrodiol,. Chitosan powder, in a preset molar ratio, was added to the reacting mixture. Structure and thermal properties were investigated by FT-IR, DSC and dynamic mechanical analyses (DMA). The obtained biohybrid hydrogels show interesting structural characteristics: the insertion of chitosan in the polymeric structure induced an increase of swelling degree, modification of the structure (by FTIR), and thermal properties (by DSC and DMA). DMA analyses, performed on dry and swollen state, showed a significant increase of storage modulus with the insertion of chitosan; swelling induced a decrease of the storage modulus. Obtained results indicate the possibility to produce a range of materials with substantially different properties to be targeted to different applications.