Free-radical copolymerization of acrylic acid with 2-acryloyloxyethyl 2,4-dichlorophenoxy2acetate using 1.0 mol/L 1,4-dioxane solution and 1.5 x 10 mol/L of 2,2' azobisisobutyronitrile as initiator has been carried out at 50 degrees C. In addition to low conversion solution experiments performed to estimate the monomer reactivity ratios, three different copolymerizations over the whole range of conversions have been made. Theoretical values of cumulative copolymer composition, determined by the Mayo-Lewis terminal model, have been correlated with those experimentally obtained. Finally, the herbicide release in three different aqueous pH buffer solutions has been evaluated in heterogeneous phase. (c) 2006 Wiley Periodicals, Inc.