A fully sustainable, flexible, and degradable lignocellulose-based composite film enabled by a bio-based polyimine...

Traditionally unsustainable and nondegradable fossil-based plastics have resulted in serious environment pollution problem. Renewable and biodegradable lignocellulose biomass is a promising raw martial for developing environmentally friendly plastic alternatives. However, lignocellulose biomass itself is non-thermoplastic crosslinking networks consisting of cellulose, lignin, and hemicellulose, resulting in a huge challenge to thermoform its into plastic alternatives. Vitrimers which own dynamic network exchange character can enable polymer materials excellent thermo-processability and recyclability. Herein, a thermoforming strategy of lignocellulose biomass was successfully developed by integrating wood powders (WPs) including natural wood powder (NWP), oxidized wood powder (OWP), and aminated wood powder (AWP) into the dynamic networks of a bio-based polyimine vitrimer (Bio-PI). The resulting WPs/Bio-PI mixtures can be easily processed into a fully sustainable lignocellulose-based composite film (LCF) by hot-pressing. The obtained LCF shows good flexibility and strength with the highest tensile strain, toughness, and tensile strength of 61 %, 365 MJ m^-3, and 9 MPa, respectively. The LCF also exhibits heat-triggered re-shaping capability, ultralow water absorption ratio (<1 %), high water stability, and excellent resistance to dilute acid/alkali solutions. Moreover, the LCF can be completely chemical-degraded because of the reversible crosslinking performance of Bio-PI. Such LCF represents an environmentally friendly plastic alternative.