Browsing by Author "Hirosawa, K"
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- ItemMicroscopic solvation structure and phase behavior of thermo-responsive polymers in ionic liquids(International Conference on Neutron Scattering, 2017-07-12) Hirosawa, K; Fujii, K; Ueki, T; Kitazawa, Y; Watanabe, M; Gilbert, EP; Shibayama, MIonic liquids (ILs) are molten salts having their melting points near room temperature. ILs consist of only ion species, and thus they exhibit unique solvent properties such as high ion conductivity, negligible volatility and nonflammability. Recently,it was reported that poly(benzyl methacrylate) (PBnMA) and its derivatives show a lower critical solution temperature type phase separation in ILs. Interestingly, the phase separation temperature of the thermo-responsive polymers in IL systems strongly depends on both chemical structures of the polymer and the ILs. It indicates that macroscopic phase behavior of the systems is strongly affected by microscopic molecular interactions between polymers and ILs. In this study, we performed small-angle neutron scattering (SANS) experiments on various PBnMA derivatives in deuterated IL solutions. The interaction parameter, ? between the polymers and the ILs was estimated from the obtained SANS profiles. Here, enthalpic (?H) and entropic (?S) contributions to ? were obtained from temperature dependence of ?. As a result, it was found that ?H strongly depends on the chemical structure of the polymers and the ILs. Furthermore, microscopic solvation structure of the polymers in IL systems was investigated by high-energy X-ray total scattering measurement with the aid of molecular dynamics (MD) simulations. It was found that there is strong correlation between the value of ?H and the microscopic solvation structure.
- ItemSmall angle neutron scattering on critical polymer clusters formed with tetra-armed prepolymers(International Conference on Neutron Scattering, 2017-07-12) Li, X; Hirosawa, K; Sakai, T; Gilbert, EP; Shibayama, MSol-gel transition is one of phenomena classified to percolation transition. Percolation has been extensively investigated in 1970s – 1990s both experimentally and theoretically. By tuning the concentrations and ratio of monomers and crosslinkers, one can synthesize various critical clusters on the verge of percolation. However, most of the previous studies only focused on one critical conditions (one monomer concentration and one crosslinker ratio). Recently, we succeeded in preparation of critical polymer clusters by cross-end-coupling multi-arm prepolymers, which shows less side-reactions and generates critical polymer clusters with good reproducibility. In this presentation, we revisit this old problem by using well-tuned polymer network clusters at various critical conditions, discuss the structure of critical polymer clusters, and demonstrate some applications.