Self-healable polymer gels with multi-responsiveness of gel-sol-gel transition and degradability

Self-healable materials can recover their structures and functions upon injury, which is extremely attractive for emerging biomedical applications. In this research, P(N-isopropyl acrylamide-co-4-formylphenyl acrylate) P(NIPAM-co-FPA) with a pendant benzaldehyde group though connection with a base-labile phenolic ester bond was designed, and polymer gels were prepared with PEO dihydrazide as a crosslinker. The polymer gels formed automatically by self-catalysis but their self-healing property was dependant on cross-linking density. The self-healing property of the polymer gel improved with decreasing cross-linking density based on decreasing FPA composition, increasing molecular weight of the crosslinker, and decreasing gelator concentration. Based on the reversibility of the acylhydrazone bond, the polymer gel showed gel-sol-gel transition by variation of acidity and group ratios. Furthermore, the gels could be degraded by Na2CO3 solutions because the phenolic ester bond is base-labile.