Effect of Polymerizable Surfactants on the Tacticity of Polystyrene Obtained by Microemulsion Polymerization

ABSTRACT

The influence of polymerizable surfactants on the colloidal, molecular, and stereochemical properties of polystyrene produced by radical polymerization remains scarcely explored. In this work, styrene was polymerized by radical microemulsion polymerization using Hitenol BC10 (HBC10), Hitenol BC30 (HBC30), Noigen RN20 (NRN20), Noigen RN30 (NRN30), and Noigen RN50 (NRN50) as polymerizable surfactants. The effect of surfactant structure on polymerization kinetics, latex particle size, molar mass, and polystyrene tacticity was investigated. Monomer conversions of approximately 95% were obtained with HBC10 and HBC30, whereas nearly complete conversion was achieved with NRN30 and NRN50. In contrast, the conversion obtained with NRN20 leveled off at approximately 80%. Final latex particle diameters ranged from 31 to 46 nm. Monomodal particle‐size distributions were obtained for all systems except NRN20, which exhibited a bimodal distribution associated with particle coagulation. Weight‐average molar masses ranged from 7.5 × 10 ⁵ to 2.9 × 10 ⁶  g mol ⁻¹ . ¹³ C‐NMR analysis showed syndiotactic contents of 55%–64% for polystyrene synthesized with the polymerizable surfactants, exceeding the 50% obtained with the conventional surfactant sodium dodecyl sulfate. The highest syndiotactic tendency was observed for HBC10. The stereochemical distributions were generally consistent with a predominantly Bernoullian propagation mechanism, with racemo addition favored over meso addition, except for HBC10, whose pronounced deviation from Bernoullian statistics suggests a degree of stereochemical memory possibly associated with a more structured propagation environment at the particle interface. These results indicate that polymerizable surfactants influence not only the colloidal and molecular characteristics of polystyrene latexes but also the stereochemical distribution of polystyrene produced by radical polymerization.