A dual-dynamic crosslinking network enabled strong, flexible, self-healing, and biodegradable chitosan fiber...

The development of high-performance biomass-based vitrimers has emerged as a crucial research topic to reduce reliance on petroleum-based plastics. Achieving both high strength and toughness is essential for most biomass-based vitrimers, yet these properties typically tend to be mutually exclusive. Here we show a multifunctional composite, CFP/TAV-PI, prepared by integrating an all-natural polyimine vitrimer (TAV-PI) into chitosan fiber paper (CFP) through in-situ polymerization and heat-pressing treatments. The CFP/TAV-PI films, featuring a dual-dynamic crosslinking network of hydrogen bonds and dynamic imine bonds, achieve a tensile strength of 57.93 MPa, elongation at break of 44.66 %, and toughness of 18.00 MJ m^-3. Additionally, CFP/TAV-PI possess high transparency, self-healing ability, and thermal/chemical stability. Importantly, they are also readily degradable under both chemical and natural conditions. Our findings highlight a novel approach to prepare degradable composites with remarkable strength and flexibility, offering the potential to replace conventional plastic products.