Transparent and mechanically robust Polyvinyl-alcohol nanocomposites based on multiple cross-linked networks for paper-reinforcement Technology

Abstract

Materials based on fiber-reinforced coating have gained increasing attention due to their environmental and industrial application tracks. Polyvinyl alcohol (PVA) composites with interpenetrating cross-linked structures and abundant functional groups exhibit obvious advantages for high-performance coating. In this work, PVA multiple cross-linked network nanocomposites (MPAUs) were established using silica nanoparticles as reinforcing fillers, ingeniously synthesized boronic esters (BGTs) and blocked-diisocyanate polyurethanes (TBPUs) as cross-linkers. Briefly, SiO2 nanoparticles were evenly dispersed into PVA matrix to fabricate primary physical cross-linked network, which could promote subsequent cross-linking and esterification effects. After deblocking, TBPU molecules were grafted onto PVA chains via radical polymerization. Meanwhile, the borate ions B(OH)4− generated by the multi-stage ionization of BGT were re-coordinated with the hydroxyl groups of PVA matrix. These two effects further afforded secondary chemical cross-linking networks and coordination cross-linked domains. The mechanical and microstructural properties of MPAUs were assessed with respect to their cross-link density and multiple cross-linked network structure. Of note, the formation of multiple-cross-linking network enabled MPAU films with substantial enhancements in mechanical strength and toughness, reaching to 58.9 MPa and 79.5 MJ/m3, respectively. The results of application studies indicated that the obtained MPAUs could integrate with cellulose paper to accomplish excellent physical strength and surface properties. In conclusion, this work paves the way to fabricate multifunctional nanocomposites, which enriches the commercial value of versatile paper-based materials.