STUDY OF STYRENE POLYMERIZATION IN THE SELF-ORGANIZING AMPHIPHILIC SYSTEM : WINSOR TYPE I

Abstract

This thesis presents the studies of styrene polymerization in a new polymerization system, herein referred to as a Winsor I-like (WL) system. The new WL system is successfully used for the first time to polymerize styrene using the redox initiator APS/TMEDA. The system consists of a microemulsion in a lower phase, while an excess styrene is topped up in the upper phase. The polymerization takes place only in the microemulsion phase where a water-soluble redox initiators APS/TMEDA is present. The styrene phase acts only as a single monomer reservoir. Unlike the microemulsion polymerization which requires higher concentrations of surfactant, the new WL system needs only about 1.0 wt% DTAB for producing as high as 15 wt% polystyrene microlatex. This 1s m contrast with the normal microemulsion polymerization of styrene, which usually requires about 10 wt% DTAB in order to produce about 8 wt% polystyrene of a stable latex. Rather monodispersed polystyrene particles (Dw/Dn=1.13) were obtained from the system that produced nanoparticles smaller than 100 nm in diameter at room temperature using only 1 wt% DTAB, 1 mmol/L of redox initiator (equimolar APS/TMEDA). The factors that affect the polymerization are the initiator concentration, polymerization temperature and the amount of styrene in the upper-oil phase. The stability of final polystyrene microlatex is affected by the stirring in the microemulsion phase, the concentration of redox initiator, polymerization temperature, the amount of styrene in the upper phase and the concentration of DTAB in the microemulsion phase. The higher styrene contents ( 10-15 wt%) for producing stable polystyrene latexes can only be obtained from the WL polymerization using a low initiator concentration (1 mM equimolar of APS/TMEDA) at a low polymerization temperature (30°C). Three types of polymerization rate-conversion curves are observed in this new polymerization system. The possible polymerization mechanisms are discussed. The continuous nucleation and the chain transfer termination may be responsible for broadening the particle sizes distribution. A paper entitled "Polymerization of Styrene in a Winsor I-like System" resulting from this work has been published in Langmuir, 10,2197-2202 ( 1994 ).