Hydrogen-bond driven formation of microstructured pressure sensitive adhesives (PSAs) with enhanced shear resistance

Acrylic based pressure sensitive adhesives (PSAs) are a widely used class of adhesive in which the suitability for a given application is heavily dependent on a delicate balance of the viscoelastic properties of the material. In this work, we present a strategy for the H-bond directed structural reinforcement of acrylic PSAs with enhanced shear resistance. The system is composed of a water-based acrylic polymer dispersion functionalized with pyrrolidone groups, and tannic acid, a natural occurring polyphenol, dissolved in water. It is demonstrated that during the drying of the dispersions, the H-bonds between the pyrrolidone groups in the polymer particles and the hydroxyl groups of TA in the aqueous phase promote the spontaneous formation of a percolating TA network around the soft acrylic polymer particles. Even when present as a fraction of a percent of the total formulation, the synergistic combination of the H-bond network and the structural reinforcement leads to PSAs with substantially improved shear resistance, whilst maintaining good peel strength. Unlike most approaches to improving shear resistance of acrylic PSAs, the proposed strategy is particularly interesting in that it offers the potential for post-synthesis tuning of the adhesive behavior of the PSA.