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 Na+-MMT 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. (C) 2005 Elsevier Ltd. All rights reserved.