Controlled release of herbicides bound to poly[oligo(oxyethylene) methacrylate] hydrogels

Abstract

A series of polymeric hydrogels containing different oxyethylene oligomers has been prepared by radical polymerization of oligo(oxyethylene) methacrylate monomers in the presence of different amounts of N, N′-methylenebisacrylamide as crosslinking agent or acrylamide as hydrophilic comonomer. Systemic herbicides, such as 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid, were covalently supported on the polymeric hydrogels by esterification of the side chain hydroxyl groups. In the investigated samples, swelling in water depends mainly on the length of the oligo(oxyethylene) side chains, the content of hydrophilic comonomer and, to a minor extent, on the degree of crosslinking. Herbicide loading produces a substantial drop in the water uptake by the polymer. The release of herbicides, investigated at room temperature in water at different pH values, is very much affected by alkalinity and to a lesser extent by the polymer structure.