Kinetic events of (micro)emulsion polymerization of styrene

Abstract

Integro-differential (ID) model approach has been tested on the o/w microemulsion polymerization (MEP) of styrene (S). The effect of macroinimer (MIM), time and temperature on the MEP kinetics has been modeled. The S-shaped conversion–time curves appear in the studied runs. A presented approach with four states (conversion, active and inactive particles and micelles) is followed with conversion, temperature and additive concentration, to recognize the main events occurring in styrene MEP. The existence of diffusive (vitreous) effects has been questioned. Furthermore, the problem of understanding some underlying phenomena in MEP is addressed, with an ID approach combining simple notions and concepts from microemulsion kinetics. The procedure is applied mostly to previously reported experimental data on the polymerization of styrene (S) initiated by peroxodisulfate and peroxodisulfate/sodium thiosulfate (STS) redox system, stabilized with ionic emulsifier sodium dodecyl sulfate (SDS). It was found that the nucleation rate does not follow a linear, but a bell-shaped curve. This is the reason why the rate of polymerization versus conversion curve shows the two nonstationary-rate intervals. The addition of MIM decreases both the particle nucleation and the growth events.