Basic Research and Development of Model Polymers for Optical Use with Low Birefringence

为了阐明应变诱导双折射的起源和松弛机制，我们测量了30多种聚合物材料的动态粘弹性和振动变形中的动态双折射。对一系列乙烯基聚合物的系统研究表明，双折射和弹性模量由两个弛豫成分组成：一个在高温和长时间起主导作用，另一个在低温和短时间起主导作用。从极化率的各向异性和单体单元的取向出发，推导出了与两个弛豫模相关的双折射估算公式。将理论表达式与观测结果相结合，得到了一种从单体单元的几何各向异性估计取向函数，然后从分子结构估计应力光学系数的方法，并根据预测的双折射程度与分子结构之间的关系合成了几种聚合物。一些聚烯烃，包括主链上的环状结构，被揭示为低双折射。氢化聚苯乙烯也被发现是低双折射的。从光学性能和机械性能两方面考虑，不同氢化度的氢化聚苯乙烯混合物是一种性能优良的材料。

In order to clarify the origin and the relaxation mechanism of strain-induced birefringence, we measured the dynamic viscoelasticity and the dynamic birefringence in oscillatory deformation for more than 30 polymeric materials. Systematic studies for a series of vinyl polymers revealed that the birefringence as well as the modulus are composed of two relaxational components ; one dominant at high temperatures and long times and the other at low temperatures and short times. An equation was derived to estimate the birefringence associated with two relaxation modes from the anisotropy of polarizability and the orientation of monomer units. By combining the theoretical expression and the observed results, a method was obtained to estimate the orientation function from the geometrical anisotropy of monomer unit and then to estimate the stress-optical coefficient from the molecular structure.According to the predicted relation between the degree of birefringence and molecular structure, a few polymers were synthesized. Some of the polyolefins including cyclic structures in the main chain were revealed to be low birefringent. Also hydrogenated polystirene was found to be low birefringent. It was suggested that mixtures of hydrogenated polystirene of different degrees of hydrogenation would be excellent materials in view of the optical as well as the mechanical quality.