NMR-STUDIES OF SOL-GEL TRANSITION AND MOL ECULAR-DYNAMICS IN SYSTEMS BASED ON METHYL-METHACRYLATE METHACRYLIC-ACID COPOLYMER

The NMR measurements showed that the sol-gel transition in systems bas ed on methyl methacrylate-methacrylic acid copolymer proceeds via thre e stages. In the first stage, the diffusion of plasticizer causes devi trification of the polymer; simultaneously, the aggregates of latex pa rticles disassemble on the macroscopic scale. The second stage feature s the formation of a gel having non-equilibrium structure, which exper iences final rearrangement in the third stage. The ratio of the relaxa tion rates at these stages depends on the plasticizer content. Upon co mpletion of the sol-gel transition, the system becomes multiphase: it contains elastomeric domains, crystalline (or glassy) phase, and inter mediate regions. NMR spectroscopy provides a means for determining the ultimate compatibility of polymer and plasticizer using small samples . The macromolecules exhibit higher mobility at lower temperatures, wh ile molecules of plasticizer are more mobile at high temperatures. The inversion of mobility occurs approximately at the melting temperature of the plasticizer.