Thermal analysis and NMR studies of methyl methacrylate (MMA)-methacrylic acid copolymers synthesized by an unusual polymerization of MMA

Methyl methacrylate-methacrylic acid (MMA-MAA) copolymers were prepared fro m the polymerization reaction of the methyl methacrylate (MMA) monomer with concentrated nitric acid (65% HNO3) at different reaction times in the abs ence of other reagents in the reaction mixture. The hydrolysis degrees of t he MMA-MAA (sodium salts) copolymers estimated by thermogravimetry (TG) cor roborated the data obtained by chemical titration. By calorimetry (DSC), a relationship between the glass transition temperature (T-g) and the hydroly sis degree was obtained. The results presented a deviation from linear beha vior and it was related to the strength of the interactions involved in the copolymer chains. The equation that relates the glass transition temperatu re to the interaction parameter, chi, for miscible binary polymer blends wa s applied for the MMA-MAA copolymers and demonstrated the composition depen dence of chi. The molecular mobility was determined by nuclear magnetic res onance (NMR) in the solid state and through the proton spin-lattice relaxat ion time in the rotating frame. The NMR data were in a good agreement with the results obtained by calorimetry. (C) 2000 John Wiley & Sons, Inc.