Ionogenic polymer pro-herbicides based on quaternized poly[oligo(oxyethylene) methacrylate]s. Synthesis and herbicide release

The preparation and structural characterization are described of polymeric proherbicides consisting of 4-chloro-2-methylphenoxyacetic acid (CMPA) ionically bound to linear and crosslinked polymer matrices based on oligo(oxyethylene) monomethacrylates (DPn oligooxyethylene: 2, 4 and 8), containing quaternary onium groups (%-mol: 8-60).CMPA loading was carried out by an ion-exchange procedure and CMPA contents in the range 0.15-0.45 mmol/g of dry polymer were attained. The loaded polymer samples displayed typical moderate to strong hydrogel character. The herbicide release, performed in water medium at controlled pH (4, 7 and 9) and saline content, reached after three months a 55% value at the best. No definite correlation between structural parameters and release behaviour can be drawn, whereas alkaline conditions seem to favourably affect the herbicide release. The release profiles can be reproduced by a best fitting based on the concurrence of two exponential decay processes differing by three orders of magnitude in their absolute rates