Linear and Star-Shaped Polystyrene-block-poly(sodium glutamate)s as Emulsifiers in the Heterophase Polymerization of Styrene

Abstract

Linear and hetero multiarm polystyrene-block-poly(sodium dl-glutamate) copolymers were used as emulsifiers in the radical emulsion polymerization of styrene in order to investigate the impact of the stabilizer topology on the main latex properties, namely average particle size, polydispersity, electrolyte stability, and electrophoretic mobility of particles, in dependence of the electrolyte concentration and pH. Compared to the linear analogues (dH = 100−220 nm, PDI < 1.04), the star-shaped stabilizers yield smaller latexes particles (dH = 70−130 nm) with broad or even bimodal distributions (PDI > 1.13), which indicates a higher stabilizing efficiency and the ability to stabilize a second generation of particles. The topology of the stabilizer affects as well the critical coagulation concentration of the latex, which is 1.0 M NaCl for linear and 0.2 M for branched copolymers. The observed stability of the latexes against electrolytes and the mobility of particles support an electrosteric stabilization of the particles.