Scattering from deformed swollen gels with heterogeneities

(Received 15 July 1991, accepted 9 October 1991)

Abstract
When elastic materials are anisotropically deformed, heterogeneities in stiffness generally produce long-range density variations. The effect is particularly enhanced in swollen gels. We calculate the structure factor from such frozen denstiy deviations under general affine deformations. It is maximized in the most stretched direction, whereas that from the thermal fluctuatins is minimized in the same direction. As a result, under uniaxial extension, a crossover occurs from normal to abnormal butterfly scattering patterns wiht increase of the strength of inhomogeneity or the swelling ration in accord with recent scattering experiments. Furthermore, scattering patters under shear deformation closely resemble those from phase-separating semidilute polymer solutions under shear flow.