Structure and dynamics of poly(N-isopropylacrylamide)-clay nanocomposite gel

The structure and dynamics of poly(N-isopropylacrylamide) (PNIPA)-clay nanocomposite (NC) gels have been investigated by small-angle neutron scattering and dynamic light scattering in order to account for their high strength and high deformability. The structure of clay dispersion in water was an assembly of clay platelets 300 Angstrom in diameter and 10 Angstrom thick. The structure factors of the clay dispersions were reduced to a master curve by normalizing with the clay concentration, C-clay, even across its sol-gel transition. On the other hand, the structure factors of the NC gels cannot be represented with a simple addition of the structure factors of the components, but with a sum of Lorentz (L) and squared-Lorentz (SL) functions. It was found that the SL term, indicating the gel inhomogeneities, becomes dominant by increasing C-clay. The chain dynamics of the gels was found to be similar to the conventional PNIPA gels chemically cross-linked with bis-acrylamide.