Sprayable oxidized polyvinyl alcohol with improved degradability and sufficient mechanical property for fruit preservation

Abstract

Besides limited preservation capacity and low biosafety, traditional fruit preservation procedures exacerbate "white pollution" because of utilizing excessive plastic. Herein, an environmentally-friendly one-pot method is developed to obtain degradable polyvinyl alcohol (PVA), where hydroxyl radicals generated through reaction between hydrogen peroxide (H2O2) and iron ions exert a function of oxidizing PVA. Such oxidized PVA (OPVA-1.0) with amounts of ketone groups, reduced crystallinity, and short molecular chains is completely degraded into H2O and CO2 after being buried in soil for ~60 days. An improvement of degradation rate does not weaken mechanical properties compared to other modified PVA films, because adverse effect of decreased crystallinity on mechanical performance is offset by ions coordination. Tensile strength or toughness of the OPVA-1.0 is enhanced instead, due to internal multi-level interactions including molecular chains entanglement, hydrogen bonding, and metal coordination bonds. More interestingly, the OPVA-1.0 is water-welded into various products in a recyclable way owing to reversible physical bonds, and it is sprayed, dipped, or brushed conformally onto different perishable fruits to delay the ripening by 5−14 days. Based on cellular biocompatibility and mice biosafety evaluations, the OPVA-1.0 acquired by such facile oxidation strategy is demonstrated to alleviate "white pollution" and delay fruits ripening effectively.