Kinetics of styrene emulsion polymerization in the presence of montmorillonite

The effect of the pristine sodium montmorillonite (Na-MMT) on the styrene emulsion polymerizations with different concentrations of SDS ([SDS]) was investigated. At constant [SDS], the polymerization rate is faster for the run with 1 wt.% Na-MMT compared to the counterpart without Na-MMT. Micelle nucleation predominates in the polymerizations with [SDS] = 13 mM. On the other hand, the contribution of the polymerization associated with the Na-MMT platelets increases significantly when [SDS] decreases from 13 to 9 mM. At [SDS] (e.g., 2 mM) < CMC, homogeneous nucleation controls the particle formation process and polymerization kinetics. Moreover, the contribution of the NaMMT platelets that act as extra reaction loci to the polymerization kinetics is even comparable to the run in the absence of Na-MMT. The resultant polymer particle size, polymer molecular weight and zeta potential were characterized and a preliminary model was developed to qualitatively study the differences between the polymerizations in the presence and absence of 1 wt.% Na-MMT. 2005 Elsevier Ltd. All rights reserved.