SMALL-ANGLE NEUTRON-SCATTERING IN POLY(VINYL ALCOHOL) HYDROGELS

Neutron and light scattering observations are reported for chemically cross-linked poly(vinyl alcohol) hydrogels differing in cross-link density and for the corresponding semidilute polymer solution. The small angle neutron scattering spectra could be decomposed into a static and a dynamic component, the former being assumed to follow an Ornstein-Zernike form and the latter a stretched exponential. Macroscopic swelling pressure and shear modulus measurements were also performed on the same gels to provide an estimate of the scattering from dynamic concentration fluctuations in the zero wave vector limit. Introduction of cross-links increases the amplitude of the static concentration fluctuation component. The fluctuating part of the scattered intensity, independently determined by quasi-elastic and static light scattering measurements, is in close agreement with that estimated from the dynamic contribution of the neutron spectra.