Water-triggered adaptive polyvinyl alcohol-polysaccharide supramolecular films with switchable structural and adhesive functions

Polyvinyl alcohol (PVA) based films experience significant degradation in mechanical properties under high humidity conditions. This study employed ultrasonic-assisted assembly technology, utilizing the electrostatic interaction between chitosan and pectin to prepare a hybrid polysaccharide polymer (CP). Subsequently, it was blended with PVA to develop a PVA-CP supramolecular film which exhibited both water-responsive and adhesive properties. Benefiting from the reinforcement of PVA crystalline domains by a locally ordered network structure, the PVA-CP (7꞉3) film maintained a tensile strength of 46 MPa after 48 h of water immersion. It is noteworthy that water-responsive adaptive PVA-CP films can be transformed from bioplastics into high-performance adhesives through water activation and hot-pressing. When used to bond poplar and eucalyptus veneers in plywood production, its performance surpasses the requirements for Class II panels of plywood. Furthermore, this film demonstrated significant application potential in multilayer plywood and exhibited an overall lower environmental footprint and cost compared to conventional petroleum-based films. This design strategy broadens multifunctional application prospects for eco-friendly, high-performance and recyclable bioplastic films. The core advantages of the films are water-responsive adaptability and bonding properties.