Strain-birefringence of a polyelectrolyte gel

Results of measurements of the stress-optical coefficient and the Young elasticity modulus of -SO3- and -CH2-SO3- polyelectrolyte gels are reported. Upon stretching the gels become birefringent. The birefringence is assumed to be caused by a partial orientation of optical anisotropic structures formed by highly cross-linked regions which are embedded in nonbirefringent regions with a lower concentration of cross links. These results give support to a proposed structural model of the gels which takes into account small-angle and ultrasmall-angle X-ray scattering data as well as information about the transport properties of the gels in form of membranes.