Polystyrene(1)/poly(butyl acrylate-methacrylic acid)(2) core-shell emulsion polymers. Part I. Synthesis and colloidal characterization

Polystyrene (PS) (1)/Poly(n-butyl acrylate (BA)-methacrylic acid (MAA)) (2) structured particle latexes were prepared by emulsion polymerization using monodisperse polystyrene latex seed (118 nm) and different BA/MAA ratios. Three main aspects have been investigated: i) the polymerization kinetics; ii) the particle morphology as a function of reaction time; iii) the distribution of MAA units between the water phase and the polymer particles.The amount of MAA in the shell copolymer was found to be the main factor controlling the particle shape and morphology. The shape of the structured particles was, generally, non-spherical, and the shape irregularities increased as a particles was, generally, non-spherical, and the shape irregularities increased as a function of reaction time. At the beginning of the second stage reaction, new small particles were observed, which coalesced onto the PS seed as the polymerization proceeded. The distribution of the MAA groups in the latex particles and the serum was analyzed by alkali/back-acid titration, using ionic exchanged latexes. No MAA groups were detected in the latex serum. Due to the lowTg of the BA-MAA copolymers, alkali conductimetric titrations accounted for all the MAA groups on and within the polymer particles. Therefore, for these systems, this method is not only limited to a thin surface layer, as it is often assumed.