Zwitterionic monomers as stabilizers for high solids content polymer colloids for high-performance coatings applications

Despite the huge and increasing application of high solids content polymer colloids for coating application, there are few challenges that still limit their full potential. The most emerging one is the use of surfactants for colloidal stabilization that affects negatively the coating performance. Moreover, due to their particulate nature, the waterborne dispersions presents lower mechanical performance with respect to the solvent-based counterparts. In this work, the possibility of use of zwitterionic monomers that contain multiple ionic functional groups, to provide colloidal stability of industrially relevant high solids content waterborne dispersions (50 %) was investigated. For that aim, small amount of 2-(methacryloyloxy) ethyl dimethyl-(3-sulfopropyl) ammonium hydroxide (DMAPS) zwitterionic monomer was employed to form in-situ stabilizing units during methyl methacrylate/n-butyl acrylate (MMA/BA) emulsion polymerization. The main challenge was to avoid DMAPS aqueous phase polymerization, hence, to achieve its high incorporation onto hydrophobic MMA/BA polymer particles, a key requirement for colloidal stabilization. Certainly, high DMAPS incorporations were achieved (>50 %) providing excellent colloidal stability, and due to the stiff nature of the multiple ionic group, impressive improvement of mechanical properties of the resulting coating films. Additionally, DMAPS presence in the polymer chains conveys to the coatings enhanced water resistance and high humidity permeation, paving a way towards powerful barrier coatings application.