title: Microphase separation in nanocomposite gels.
abstract: Microphase separation in poly(N-isopropylacrylamide)(PNIPA)-clay nanocomposite hydrogels (NC gels) is investigated by means of contrast-variation small-angle neutron scattering (CV-SANS) and dynamic light scattering (DLS). By using CV-SANS, it is revealed that microphase separation occurs in NC gels above the lower-critical solution temperature (LCST) of PNIPA aqueous solutions. The observed partial scattering functions show that only the spatial distribution of PNIPA chains is highly distorted by microphase separation and PNIPA chains are preferentially adsorbed on the clay surfaces, where the PNIPA-rich phase forms nanoscaled bicontinuous structure mediated by the clay particles. Additional DLS measurements for dilute solutions with PNIPA and/or the clay nanoparticles confirm that aggregation of PNIPA above the LCST is dramatically suppressed by addition of clay particles. Based on these observations, we conclude that strong affinity between the polymer and clay has a significant effect on the phase separation in NC gels and allows one to tune the length scale of the phase separation phenomenon by clay concentration.
authors: Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, Tokai, Ibaraki 319-1106, Japan.
authors: Noboru
authors: N
authors: Osaka
authors: Hitoshi
authors: H
authors: Endo
authors: Toshihiko
authors: T
authors: Nishida
authors: Takuya
authors: T
authors: Suzuki
authors: Huan-jun
authors: HJ
authors: Li
authors: Kazutoshi
authors: K
authors: Haraguchi
authors: Mitsuhiro
authors: M
authors: Shibayama