One-pot synthesis of dibenzaldehyde-terminated poly(ethylene glycol) for preparation of dynamic chitosan-based amphiphilic hydrogels

In order to synthesize dynamic amphiphilic hydrogels, in the first step, dibenzaldehyde-terminated telechelic poly(ethylene glycol) (PEG-DA) was synthesized via simple one-pot method by using hexamethylene diisocyanate and para-hydroxybenzaldehyde. In the second step, 4-arm star-shaped polycaprolactone tetraaldehyde (4sPCL-TA) was synthesized in three steps. All of the synthesized prepolymers and functionalization reactions were characterized by H-1-NMR and FT-IR spectroscopy. Finally, a series of new dynamic amphiphilic hydrogels were prepared through dynamic covalent Schiff-base linkages by simply mixing nontoxic chitosan, PEG-DA and 4sPCL-TA solutions. The chemical structure, morphology, thermal properties, gel degradation, mechanical performance, swelling behavior and self-healing capability of hydrogels were investigated. The obtained results showed that the hydrogels present suitable self-healing performance without any external stimulus. These properties of hydrogels can be attributed to covalent Schiff base linkages between the aldehyde and amine groups of prepolymers. Moreover, the hydrogels displayed pH-dependent degradation behavior. Swelling degree and degradation rate of hydrogels decreased with introducing of 4sPCL-TA in hydrogel networks. In addition, the thermal and mechanical properties of hydrogels were improved with incorporation of 4sPCL-TA into the network structure.