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 den sity 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-Z ernike form and the latter a stretched exponential. Macroscopic swelli ng pressure and shear modulus measurements were also performed on the same gels to provide an estimate of the scattering from dynamic concen tration fluctuations in the zero wave vector limit. Introduction of cr oss-links increases the amplitude of the static concentration fluctuat ion component. The fluctuating part of the scattered intensity, indepe ndently determined by quasi-elastic and static light scattering measur ements, is in close agreement with that estimated from the dynamic con tribution of the neutron spectra.