A survey of alkyl methacrylate latexes as aqueous catalytic media

Cationic polymer latexes serve as catalytic media for the hydrolysis of p-n itrophenyl esters by providing a more lipophilic environment into which the se compounds can partition from the aqueous phase. The latex quaternary amm onium ions attract high local concentrations of reactive or catalytic anion s into the water-swollen particles. We synthesized 32 different methacrylat e and styrene latexes via a parallel synthetic route and tested their activ ities for the hydrolysis of p-nitrophenyl hexanoate. The most active latex is a copolymer of 75% 2-ethylhexyl methacrylate and 25% vinylbenzyl chlorid e that was quaternized with tributylamine. The rate of hydrolysis at 30 deg rees C is 17 times faster using 0.6 mg mL(-1) of latex in pH 9.4 berate buf fer relative to control experiments that lacked polymer latex. Analysis of the kinetics shows that the latex activities depend primarily on the latex/ water partition coefficients of p-nitrophenyl hexanoate. The latexes also p romote the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate(B-NBIC) in aqueous media, and 0.6 mg mL(-1) of the latex from 75% 2-ethylhexyl methac rylate and 25% vinylbenzyl chloride quaternized with tributylamine gave an observed rate constant 10 400 times that in water alone. The rate accelerat ions of 6-NBIC decarboxylation are due to both favorable partitioning into the latex and faster intraparticle rate constants.