STRAIN-BIREFRINGENCE OF A POLYELECTROLYTE GEL

Results of measurements of the stress-optical coefficient and the Youn g elasticity modulus of -SO3- and -CH2-SO3- polyelectrolyte gels are r eported. Upon stretching the gels become birefringent. The birefringen ce is assumed to be caused by a partial orientation of optical anisotr opic structures formed by highly cross-linked regions which are embedd ed in nonbirefringent regions with a lower concentration of cross link s. These results give support to a proposed structural model of the ge ls which takes into account small-angle and ultrasmall-angle X-ray sca ttering data as well as information about the transport properties of the gels in form of membranes.