| Abstract: | Continuously uniform latices were applied in an experimental study of molecular weight development in constant-rate styrene emulsion polymerization. The formulation around which this study centered exhibited Smith-Ewart, case II kinetics from zero to about 60% conversion with a constant conversion rate of 13 ± 2%/hr and a final particle diameter of 2300 Å. By utilizing an inhibitor perturbation technique, we directly confirmed that free radicals are generated from K2S2O8 by a first-order process with 100% efficiency. We further confirmed that, in contrast to current theories for constant rate polymerization, both the instantaneous values of M?n and M?v may increase 6- to 9-fold. Little or no chain branching is evidenced. We interpret these findings to mean that radicals are not utilized with 100% efficiency in emulsion polymerization. |
