pH-Responsive Carboxylated Latexes: Switching between Stabilization and Destabilization

Abstract

Waterborne polymeric dispersions are common additives used in a broad variety of applications, for example, in waterborne adhesives, architectural coatings, and cementitious applications. For some of these applications, the polymer is often supplied in a dry form. This study aims to explore the feasibility of incorporating responsive moieties to obtain polymer latex with reversible coagulation properties, allowing for restabilization of particles in the form of a dispersion from isolated polymer. The challenges are to have a switchable colloidal stabilizing system to precisely control the coagulation and restabilization process on-demand and to limit sintering and interdiffusion of soft polymer particles (with a glass transition temperature Tg < 25 °C) when isolated. Carboxylated latexes with variable Tg’s (17-25 °C) and acid content (1-2.5 wbm%) were synthesized through surfactant-free emulsion copolymerization of vinyl acetate, vinyl neodecanoate (VeoVa10), and methacrylic acid. These latexes were coagulated by lowering the pH and filtration of the resulting slurry allowed removal of (most of) the water. The isolated polymer was then restabilized under varying conditions to give a polymer dispersion.