Analysis of the Kinetics of Hydrolysis of p-Nitrophenyl Alkanoates in Colloidal Polymer Dispersions by an Ion-Exchange Model

• DOI: 10.1021/la9905665
• Publication Date: 2002-07-26T06:04:16Z
• Authors: Paul D. Miller; H. Olin Spivey; Stephanie L. Cope...; Rebecca Sanders; Andrea Woodruff; David Gearhart; Warren T. Ford
• Keywords: 01 natural sciences; 0104 chemical sciences

Rates of hydrolyses of p-nitrophenyl acetate, hexanoate, and octanoate in borate buffer solutions at 30 °C are 2.3−16.5 times faster in the presence of 1.2 mg mL-1 quaternary ammonium ion exchange latex particles than those obtained in water alone. The latexes were constructed by emulsion copolymerization of styrene, butyl methacrylate, or 2-ethylhexyl methacrylate with 25 wt % vinylbenzyl chloride (VBC), 1% divinylbenzene, and 1% styrylmethyl(trimethylammonium chloride) followed by quaternization of the VBC units with either trimethylamine or tributylamine. Analysis of the kinetics as a function of particle concentration, pH, and buffer concentration using an ion-exchange model provided partition coefficients of the p-nitrophenyl esters, intraparticle second-order rate constants, and ion-exchange selectivity coefficients. The major contributors to the enhanced rates are the partition coefficient favoring absorption of the p-nitrophenyl ester into the latex by a factor as large as 90 000 and intraparticle...