Stress relaxation and hysteresis of nanocomposite gel investigated by SAXS and SANS measurement

The stress relaxation phenomena of nanocomposite gel (NC gels) after uniaxial elongation was investigated by time-resolved small-angle scattering techniques of neutrons and X-rays. Nanocomposite gels consist of clay platelets and poly(N-isopropylacrylamide). It was found that clay oriented instantly and polymer chains were elongated along the stretching direction by elongation, followed by gradual process of peeling-off of adsorbed polymer chains on the clay platelets. When the specimen was held in the deformed state, stress relaxation was observed. This was mainly ascribed to peeling-off of polymer chains. When the strain of the specimen was removed, the polymer chains tended to be adsorbed again to the surface of the clay platelets. The deformation mechanism of NC gels is discussed on the emphasis of the peeling-off and peeling-on process of polymer chains.