Structure of nanocomposite hydrogel investigated by means of contrast variation small-angle neutron scattering

Endo, Hitoshi; Nishida, Toshihiko*; Shibayama, Mitsuhiro*; Li, H.-J.*; Haraguchi, Kazutoshi*

Poly(N-isopropylacrylamide) (PNIPA)clay nanocomposite hydrogels (NC gels) possess extraordinary superior mechanical properties. We have investigated the structure of NC gel by means of contrast variation small-angle neutron scattering (CV-SANS) technique. By applying CV-SANS in a sophisticated manner, the partial scattering functions of each component can be decomposed quantitatively. The extracted partial scattering functions of clay, polymer, and the polymer-clay cross-term were analyzed in detail, and the selective interaction between clay and polymer is revealed. On the basis of these structural observations, it is confirmed that the clay nanoparticles serve as 2-dimensional cross-linkers. Furthermore, the detailed structure of uniaxially-stretched NC gel was also studied by applying CV-SANS, and microscopic origin of the deformation mechanism of NC gel was explored.