Kinetics and morpholgy dtudy of staged emulsion polymerization of styrene

Abstract

The polymerization kinetics and the morphology of heterogeneous composite latex particles which were prepared by PVC- and PMMA-seeded styrene emulsion polymerization were studied. Batch, swelling-batch polymerization methods were employed for kinetic study and semi-batch method was used for the morphological study. To determine the conversion of monomer the gravimetric method(TSC) was utilized and the change in the particle morphology was followed with TEMs of the diluted latex and the $RuO_4$-stained thin sections of composite particles. Scanning electron microscopy was used for the three dimensional shapes of particles. In PMMA-styrene systems the monodispersed PMMA latexes were used as the seed latexes. In PMMA-styrene system the rate of polymerization was found to be independent of the swelling time and pH of polymerization medium. And the rate of polymerization per particle was increased with the initiator concentration. The rate was linearly proportional to the diameter of seed latexes and the dependence was increased with the polymerization temperature. However the rate was decreased with the addition of chain transfer agent ($CHBr_3$) because of the easy desorption of the transferred radicals from the polymerizing particles. The activation energy of polymerization was 53.2 KJ/mol and the propagation rate constant was 330 ℓ/(mol. sec). The latter was calculated from Smith-Ewart Case 2 theory of PMS-46 polymerized at 60℃. IN PVC-styrene system the rate of polymerization was indirectly estimated from the peak time. In this case the rate of polymerization was independent of the swelling time and the initiator concentration, and it was increased along with the agitation speed. But the strong acidic condition of polymerization medium and the addition of isoprene, DVB or $CHBr_3$ slowed down the rate of polymerization. Anchoring effect of ionic terminal functional group, originated from ionic initiator, and their concentration were found to be the main facto...