Radical copolymerization studies of an amphiphilic macromonomer derived from Triton X-100. Reactivity ratios determination by in situ quantitative H NMR monitoring

This article deals with the estimation of the reactivity of a novel methacrylic macromonomer with amphiphilic character derived from Triton X-100 (MT) in radical copolymerisation reaction with acrylic acid (AA). Two approaches to estimate the reactivity ratio of the macromonomer are described. The first involves the use of the Jaacks equation valid for systems with a large excess of one of the comonomers and leads to r_AA=0.31. The second method uses a low molecular weight model monomer (MTm) that reproduces the chemical structure of the macromonomer. A non-linear fitting of the experimental data of the system MTm-AA to an integrated form of the copolymerisation equation which describes the terminal model postulated by Mayo and Lewis, gave reactivity ratio values of r_MTm=2.5 and r_AA=0.30. The results obtained from the two estimations suggest that methacrylic double bond reactivity is not affected by poly(oxyethylene oxide) chain length. In situ quantitative ¹H NMR analysis was used to monitor monomer consumption and therefore to follow the course of the copolymerisation reaction in both approaches.