One-pot synthesis of branched poly(methacrylic acid)s and suppression of the rheological "polyelectrolyte effect"

A novel synthesis of branched poly(methacrylic acid)s (PMAAs) is reported via conventional solution free radical polymerization of MAA with divinylbenzene (DVB) as the branching comonomer. Controlled levels of dodecanethiol (DDT) have been used successfully to inhibit network formation and gelation. Quantitative methylation of the branched polymers has been achieved using trimethylsilyldiazomethane, and subsequent H-1 NMR spectroscopic analysis of both the acid polymers and their methyl esters has allowed quantification of their molecular composition. Characterization of the branched architecture was carried out using dual detection size exclusion chromatography (DDSEC) and was confirmed by H-1 NMR spectroscopic analysis. A pH dependence study of the dilute solution reduced viscosity of the branched poly(methacrylic acid)s in 10 Vol % MeOH/H2O has shown almost complete suppression of the polyelectrolyte effect which we attribute to the branched architecture of these macromolecules.