Small Angle Neutron Scattering Study in Multi-Component Polymer Systems: Spinodal Decomposition and Beyond

Institute for Advanced Study, Shenzhen University, Shenzhen, China In memory of Professor John Kohn at this symposium, a time resolved SANS study for the early stage of spinodal decomposition kinetics of deuterated polycarbonate/poly(methylmethacrylate) blend will be reviewed which gives a clear proof of the Cahn-Hillard-Cook theory. This early stage of spinodal decomposition kinetics has been observed starting from the dimension (q$^{\mathrm{-l}})$ comparable to the single chain radius of gyration, R$_{\mathrm{g\thinspace }}$, for a binary polymer mixture. The results provide an unequivocal quantitative measure of the virtual structure factor, S (q, $\infty $ ); the relationship of q$_{\mathrm{m}}$ and q$_{\mathrm{c}}$ through rate of growth, Cahn-plot analysis, and singularity in S (q, $\infty $ ); the growth of fluctuation of qR$_{\mathrm{g}}$ \textless 1 and intra-chain relaxation of qRg \textgreater 1. More recent study of using mixed suspensions of polystyrene microspheres and poly(N-isopropylacrylamide) microgels as a molecular model system which has a long range repulsive interaction potential and a short range attractive potential, will also be discussed. In this model system, dynamic gelation, transition to soft glass state and cross-over to hard glass state will be demonstrated and compared with available theories for glass transition in structural materials. Acknowledgements go to: Polymers Division, and NCNR of NIST, and to ICCAS, Beijing, China. Also to my colleagues: M. Motowoka, H. Jinnai, T. Hashimoto, G.C. Yuan and H. Cheng