Ultra-Strong and Proton Conductive Aqua-Based Adhesives from Facile Blending of Polyvinyl Alcohol and Tungsten Oxide Clusters

The explosive growth of binder industry spurs the development of strong adhesives with the integration of multi-functionalities as well as cost-effective and eco-friendly processability. Here, polyvinyl alcohol (PVA) and sub-nanoscale metal oxide cluster, phosphotungstic acid (PTA), both with broad commercial availability, are complexed through hydrogen bonding in water. The obtained nanocomposites demonstrate promising light transmittance and proton conductivity, and most importantly, unprecedentedly high adhesive strengths as approximate to 4 kN m(-1) for peeling strength and 8.2 +/- 1.7 MPa for single lap shear strength on typical glass substrate. The supramolecular complexation of PVA with PTA can significantly reduce its crystallinity and accelerate PVA chain dynamics for negligible internal stress and membrane shrinkage upon drying, leading to close contact with glass substrates for strong adhesion. Meanwhile, the supramolecular interaction between PVA and PTA contributes to the nanocomposites' enhanced mechanical strength and resolves the issue of cohesion failure to ensure high adhesive strengths. The fast chain dynamics also benefit rapid proton transportation, contributing to the high proton conductivities. The binder design protocol can be extended to general polymer systems integrated with desired functionalities and allows scale up processing, providing great opportunities for functional adhesives for safety glass and electronic industry.

Automated summary

In this study, nanocomposites were prepared by combining polyvinyl alcohol (PVA) and phosphotungstic acid (PTA), showing promising light transmittance, proton conductivity, and high adhesive strengths. The supramolecular complexation between PVA and PTA reduced the crystallinity of PVA, accelerated its chain dynamics, and enabled close contact with glass substrates for strong adhesion. The interaction between PVA and PTA also enhanced the mechanical strength of the nanocomposites, resolving the issue of cohesion failure.