Influence of unsaturated acid monomer on the morphology of latex particles in the preparation of hollow latex via the alkali post-treatment

Multistage hydrophilic core/hydrophobic shell latexes containing carboxyl groups were prepared via multistep seeded emulsion copolymerization, and particles with different morphologies were obtained after alkali post-treatment. Influences of the type and content of unsaturated acid monomer on the polymerization and the particle morphology were investigated based on conductometric titration and TEM observation. Results showed that the hydrophilic core/hydrophobic shell particles could be easily formed using methacrylic acid (MAA) instead of acrylic acid. When MAA was 12.2 wt % in the core latex preparation, only fine pores existed inside the alkali-treated particles. With MAA increased from 20.0 to 30.0 wt %, the alkali-treated particle morphology evolved from porous, hollow to collapse structure. When MAA further increased to 40.0 wt %, it was difficult to prepare uniform multistage particles and distinct morphologies including solid, deficient swelling, hollow and collapse structure were coexistent in the alkali-treated particles. Moreover, the forming mechanism of different morphologies was proposed. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012