Effect of colloidal particle size on catalytic activity of anion exchange gels

Cross-linked anion exchange latexes 20, 150, and 1200 nm in diameter were p repared via microemulsion, emulsion, and dispersion copolymerization, respe ctively, of vinylbenzyl chloride, styrene, and divinylbenzene followed by t reatment with trimethylamine or tributylamine. As catalysts for the unimole cular decarboxylation of 6-nitrobenzisoxazole-1-carboxylate (1) the tributy lammonium ion latexes were much more active than the trimethylammonium ion latexes. There were only small differences in the rates of decarboxylation in the three different tributylammonium ion latexes, and first-order kineti cs were found at all relative concentrations of ion exchange sites and 1 in the 20 and 150 nm particle dispersions. Retardation of the rate both early and late in the reaction using a low concentration of the 1200 nm particle s is attributed to slow mass transfer of 1 from solution to the particle su rface and to competitive inhibition by the product ion.