Optical and Mechanical Anisotropy in Crystalline Polymers

Expressions have been derived for the optical birefringence and elastic moduli of an idealized semicrystalline polymer in terms of the molecular orientation. The predicted birefringence and moduli show qualitative agreement with previous experimental data for polyethylene at low extension ratios. A result of particular interest is that this treatment predicts the observed minimum in the Young's modulus with increasing orientation.