Chemical structure of zwitterionic monomers as a tool to produce colloidally stable (meth)acrylic polymer colloids

This study investigates how the chemical structure of sulfobetaine zwitterionic monomers (ZMs) as the exclusive source of ions affects the formation of in-situ colloidal stabilizing units during emulsion polymerization of methyl methacrylate/butyl acrylate (MMA/n-BA) at 30 % solids content. Four ZMs with methacrylic, acrylic, or acrylamide functionalities and different chain lengths between two ions are examined. The effect of these structural variations on ZM incorporation onto MMA/n-BA particles was studied as a crucial issue for colloidal stability and overall polymer performance. Inversely to acrylic ZM, methacrylic and acrylamide ZMs provide improved copolymerization with MMA/BA and early creation of stabilizing units, resulting in coagulum-free colloidal dispersions with enhanced salt and freeze-throw stability due to the anti-electrolytic effect, conveyed from ZM to MMA/n-BA particles. The polymer films present enhanced mechanical properties, decreased water sensitivity and improved moisture barrier, unlocking the potential for widespread use of these emulsifier-free waterborne dispersions within coatings industry.