Characterization, chain mobility, and thermal properties of the hydrophilic poly(methyl methacrylate-co-acrylic acid) colloids

An amphiphilic colloidal copolymer containing methyl methacrylate (MMA) and sodium acrylate at different compositions was prepared by a free-emulsion polymerization method with potassium persulfate as an initiator, and it was then doped in HCl solution to obtain the acid form poly(methyl methacrylate-co-acrylic acid) (PMMAA) copolymer. The copolymers were characterized by means of gel permeation chromatography, H-1 nuclear magnetic resonance spectrometer, C-13 solid-state nuclear magnetic resonance spectrometer, infrared spectra, and differential scanning calorimeter. The copolymers have only a single, and nearly constant, glass transition temperature of 124 degrees C, at which there is no observable effect on the structure of the copolymer. The monomer reactivity ratios r(NaAA) and r(MMA) were r(NaAA) = 1.06, r(MMA) = 0.70 and r(NaAA) = 1.02, and r(MMA) = 0.63 estimated respectively by using the classical Fineman-Ross and the Kelen-TUdos methods. The results revealed that the copolymer had a tendency towards the formation of small acrylic acid blocks that have very short segments of MMA. The proton spin-lattice relaxation time in the rotating frame T-1P(H) indicated single composition-dependent for all copolymers, which imply dynamic homogeneity and a good miscibility with chain dynamics on the upper spatial scale of 3 nm existed in the PMMAA copolymer. An increase of the thermal stability of the copolymers was shown from the apparent activation energy of the thermal degradation process for the copolymers relative to the homopolymers.