Incorporation of Zwitterionic Monomers into Waterborne Polymer Dispersions

Abstract

Waterborne polymers are usually produced by emulsion polymerization using emulsifiers to providecolloidal stability. The polymer films formed from these waterborne dispersions are affected by migrationof surfactants during film formation and this has negative effects on both performance and environment.Therefore, novel strategies for surfactant-free polymeric dispersions synthesis are highly welcomed. Theobjective of this project is to synthesize stable, surfactant-free waterborne polymers at high solids contentby seeded semi-continuous emulsion polymerization using small amount of different zwitterionicmonomers to provide colloidal stability. The central focus is on attaining colloidal stability purelythrough the incorporation of chemically bonded zwitterionic moieties onto the polymer particles. Thepresence of charges within the zwitterionic monomers units incorporated onto the polymer particles isexpected to provide colloidal stability. Thereby negative effects of surfactant migration on the resultantfilm properties will be prevented. Finally, properties and performance of the polymers stabilized withzwitterionic monomers will be studied and compared to a conventionally stabilized polymer latex.In pursuit of this objective, a standard coating formulation comprising n-BA/MMA in a 50/50 weightratio was consistently used throughout the research. Nonetheless, this task presents notable challenges.Zwitterionic monomers, due to their heightened water-solubility, tend to reside within the aqueouscontinuous phase, whereas the polymer particles act as the primary sites for polymerization. Furthermore,the hydrophilic nature of the zwitterionic moieties results in an increased production of water-solubleoligomers, posing a dual negative impact. On one hand, their presence affects colloidal stability byelevating the ionic strength. On the other hand, when incorporated into the polymer matrix, theseoligomers can function as plasticizers, thereby compromising the mechanical properties of the resultingcoating film. Thus, achieving a substantial degree of zwitterionic moiety incorporation onto the polymerparticles is critical.