NMR AND VISCOELASTIC INVESTIGATIONS INTO THE STRUCTURE AND DYNAMICS OF EMULSION COPOLYMER GELS

This work deals with structural and dynamical properties of copolymer gels containing free branched chains which were prepared by styrene-bu tadiene emulsion copolymerization. The gel fraction of the emulsion co polymers was varied within a large range (15-90 %) by adding different chain transfer agents during the polymerization process. NMR experime nts were performed on homogeneous polymer films obtained by coalescenc e of the particles upon drying of the dispersions. Properties of dry e xtracted gels, gels swollen by free chains, or gels fully swollen by a good solvent were investigated to bring out the statistical structure of the gels. A time-temperature superposition principle was found to provide a good analysis of the time dependence of the transverse magne tic relaxation functions. The temperature dependence of the scale fact ors reveals the strong role played by the free chains in the system. F inally, through the description of the state of constraints encountere d by chain segments, NMR and viscoelastic features of these partly cro ss-linked systems are shown to be consistently interrelated.