DYNAMIC BIREFRINGENCE OF AMORPHOUS POLYMERS

The studies on dynamic birefringence of amorphous polymers are reviewe d. The birefringence in oscillatory deformation is related to the visc oelasticity through the stress-optical rule (SOR) in the rubbery and t he terminal flow zones. The deviation from the SOR in the glassy and t he glass-to-rubber transition zones can be described with a modified S OR, based on the assumption that the stress is a sum of two components associated with respective stress-optical coefficients. Experimental results are reviewed for 14 polymers: polystyrene, poly(alpha-methyl s tyrene), poly(2-vinyl naphthalene), polyisobutylene and 10 polymers fo r engineering plastics. The nature of various parameters is discussed in relation to the molecular structure.