Spontaneous birefringence and photoelasticity of polyacrylamide gels

Abstract During the polymerization of polyacrylamide gels, spontaneous birefringence develops. This effect provides a means of following the kinetics of the polymerization reaction, which is of first-order type. The birefringence appears to be caused by strains that develop in the gel as a result of adherence to the cell walls. Measurements are also described of the stress-optical coefficient in these gels, and the different molecular contributions to this parameter are discussed. Gels in the later stages of polymerization and fully polymerized gels display form birefringence coming from the anisotropic shape of the submolecules (statistical subunits) in the polymer chains.