One-pot polymer–clay composite reversible adhesive

Abstract

Polymer–clay composites are produced using emulsion polymerization to create water-based formulations that exhibit reversible adhesion, which is triggered by alkaline or acidic aqueous solutions. These adhesives produce lap shear strengths greater than 1 MPa on a variety of substrates. A polyanionic composite is prepared by incorporating negatively charged montmorillonite into an emulsion of styrene and butyl acrylate with poly(acrylic acid) grafted from the particles. An analogue polycationic composite is made by integrating positively charged hydrotalcite into an emulsion stabilized by the physisorption of chitosan. When two substrates are both coated with the polycationic composite, reversibility is observed under acidic conditions, whereas polyanionic composites exhibit similar behaviour under alkaline conditions. Notably, polyanionic composites fully detach from the substrates, eliminating the need for additional washing. Clays also enhance the rheological behaviour of the emulsions, increasing the viscosity at low shear rates by up to 8 and 800 times, for polyanionic and polycationic formulations, respectively. These composite adhesives are a key development for facilitating the dismantling of products and enhancing recycling efficiency.