Bio-inspired natural polyphenol cross-linking poly(vinyl alcohol) films with strong integrated strength and toughness

Polymer composites exhibit very high strength but this is usually found to be at the expense of toughness, which greatly limits their application in many fields. Inspired by the hierarchical architectures in spider silk, we attempted to combine simultaneous high strength and toughness via a hydrogen bonding network. PVA composites with tannic acid (TA) molecules were fabricated by a green and easy-to-scale-up water casting method. The results showed that the hydrogen bonding crosslinking between PVA and TA has strong effect on the Tg, crystallinity, thermal stability and mechanical properties of PVA. In addition, the PVA composite films with 3 wt% TA exhibited, simultaneously, the best tensile strength and toughness, improving by 46% and 27% compared to the pure PVA, respectively.