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.