Strain-Induced Birefringence of Amorphous Polymers and Molecular Design of Optical Polymers

Recent progress on the molecular interpretation of strain-induced birefringence for amorphous polymers over a wide time/temperature region is briefly reviewed. In the rubbery region, orientational birefringence, which is caused by the orientation of segments, is dominant, while in the glassy region, glassy birefringence also contributes to the total birefringence observed. As a result, in order to control the strain-induced birefringence in the optical resins, both the contributions should be optimized. In this Review, we explain the characteristic features of orientational and glassy contributions and how these contributions can be related to the molecular structure of the repeating units. Besides, we show that copolymerization of a ternary system is very effective in controlling the strain-induced birefringence of the optical resins.