Microemulsion Polymerization of Styrene for Obtaining High Ratios of Polystyrene/Surfactant

Abstract

A modified ternary microemulsion polymerization was successfully used to prepare nanosized polystyrene (PS) microlatexes with high PS/surfactant weight ratios of up to 14:1. Cationic surfactants used were alkyltrimethylammonium bromides, CnTAB, where n is either 12, 14, or 16. A water-soluble initiator was used for the polymerization at room temperature, with moderate stirring. The latexes obtained are bluish-opaque and have been stable now for about 8 months. The process produced rather uniform (Dw/Dn ≅ 1.10) latex particles of about 40 nm having high molar masses of PS ranging from 1.0 to 2.2 × 106 g/mol. This was obtained by first generating monomer-starved latex particles in a ternary microemulsion containing only 0.5−1.0 wt % styrene and 1.0 wt % cationic surfactant. The subsequent supply of styrene monomer to the polymerized microemulsion was delivered either through dropwise addition or via hollow-fiber feeding of monomer. The latter method was employed for the first time.