Catalysis by colloidal polymers in aqueous media

Abstract

Crosslinked polymer latexes were prepared by emulsion copolymerization of either styrene or one of 14 different alkyl methacrylates and vinylbenzyl chloride and converted to quaternary ammonium ion latexes by reaction with trimethylamine or tributylamine. As catalytic colloidal media the cation exchange latexes increased the rate decarboxylation of 6-nitrobenzisoxazole-3-carboxylate up to 10 000 times and the rate of basic hydrolysis of p-nitrophenyl alkanoates up to 16 times in aqueous dispersions at room temperature. Latexes containing either 2-ethylhexyl methacrylate as the inert component of the polymer or tributylammonium ion active sites were most active. Catalytic activity for the decarboxylation did not depend on particle size when the diameter was <1 μm. Polyampholyte latexes containing 29/18 and 25/23 molar ratios of styrylmethyl(trimethyl)ammonium cations and methacrylate anions were colloidally stable in 4 M NaCl. Catalytic activity decreased with increasing concentrations of NaCl in the dispersions, and all of the latexes except the polyampholytes coagulated at>0.1 M NaCl. Dendrimers having one hydrophobic octyl group and one hydrophilic tri(ethylene glycol) methyl ether group on each tertiary amine end were prepared from commercial poly(propylene imine) dendrimers having eight and 32 primary amine end groups and were converted to quaternary ammonium dendrimers by methyl iodide. After ion-exchange for chloride, the polycationic dendrimers increased the rate of the decarboxylation by 200–500 times the rate in pure water.