Particle kinetics and physical mechanism of microemulsion polymerization of octamethylcyclotetrasiloxane

Abstract

In the present study, the particle kinetics and physical mechanism of microemulsion polymerization of octamethylcyclotetrasiloxane (D 4) were investigated by using dodecyldimethylbenzyl ammonium bromide (DBDA) as a surfactant and n-pentane as a cosurfactant. The light transparence of the emulsion, oil–water interfacial tension and the polymerization conversion as functions of the polymerization time were recorded. Furthermore, the particle sizes and their distributions in the process were measured by using dynamic light scattering technique (DLS). The results show that there does not exist constant-rate reaction period during the polymerization. The results of DLS show that the microemulsion polymerization can be distinguished as four steps, namely (I) the dispersion period, (II) the colloid formation and reaction period, (III) the colloid reaction period, and (IV) the agglomeration period. Corresponding physical models for each period were discussed. It has been found that the nucleation occurs mostly in the swollen-micelles and the polymerization occurs mostly in the new microlatex particles for the microemulsion polymerization of D 4.