Enhanced catalytic activity of o-iodosobenzoate in poly[(styrylmethyl)hexadecyldimethylammonium chloride] latexes for the hydrolysis of p-nitrophenyl diphenyl phosphate

Six 5.0 mol% crosslinked poly[(styrylmethyl)hexadecyldimethylammonium chloride] latexes containing 8–67% quaternization were synthesized via two-stage process and used as supports for o-iodosobenzoate (IBA) catalyst in the hydrolysis of model organophosphate compound p-nitrophenyl diphenyl phosphate (PNPDPP). The hydrodynamic diameters of the cationic latexes were less than 200 nm. The rate of the hydrolysis of PNPDPP greatly increased in the presence of the cationic latex particles and strongly depended on the degree of quaternization and amount of the latex as well as pH, type of buffer, and ionic strength of the medium. As the quaternization percentage of the latexes increased, the rates of the hydrolysis increased. The pseudo-first-order and second-order-rate constants of the hydrolysis reaction carried out with different amounts and type of cationic latexes at pH 7.0, 8.0 and 9.0 in different buffer solutions at 25 °C were determined. 1.0 × 10−5 M IBA in 0.25 mg/mL of QL-67 latex enhanced the rate of the hydrolysis of 1.0 × 10−5 M PNPDPP about 5670 times in TAPS buffered solution at pH 8.0 compared to the one in buffered solution and 1590 times in the presence of IBA alone in TAPS buffered solution. The highest second-order-rate constant kcat of 21200 ± 1100 M−1 s−1 was obtained when 0.25 mg/mL of QL-67 was employed in the hydrolysis reaction at pH 8.0.

The hydrolysis rate of the organophosphate strongly depended on the degree of quaternization and amount of latex as well as pH, type of buffer, and ionic strength.Figure optionsDownload as PowerPoint slideResearch highlights
► Poly[(styrylmethyl)hexadecyldimethylammonium chloride] latexes behave as micelle-mimetic or surfactant particles.
► The latex media greatly increase the hydrolysis rate of PNPDPP catalyzed by IBA.
► The hydrolysis rate goes higher as the degree of quaternization of the latexes increases.
► The hydrolysis rate depends on the amount of latex present in the medium.