Molecular Interpretation of Dynamic Birefringence and Viscoelasticity of Amorphous Polymers
Molecular Interpretation of Dynamic Birefringence and Viscoelasticity of Amorphous Polymers
复制标题
非晶态聚合物动态双折射和粘弹性的分子解释
DOI：
10.1021/ma00114a016
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发表时间：
1995
期刊：
影响因子：
5.5
通讯作者：
E. Hwang
中科院分区：
文献类型：
--
作者：
K. Osaki;H. Okamoto;Tadashi Inoue;E. Hwang
将已发表的非晶态聚合物的动态双折射和粘弹性数据与Gao和Weiner提出的应力分子表达式进行了比较。该理论指出，应力由链取向（取向项）、围绕链轴的单体取向（旋转项）和局部应力张量的波动（波动项）的贡献组成;双折射仅由对应于前两个应力的两个项组成。实验数据表明，在玻璃态区和玻璃-橡胶过渡区的高频区的应力是归因于旋转和波动项和程度的贡献不同的聚合物物种。对于具有平坦单元的聚合物（如聚碳酸酯），波动项可以忽略，并且在玻璃态区的弛豫谱较低。对于薄的轴对称单元（如聚异丁烯）或庞大的不规则单元（如聚（2-乙烯基萘））的聚合物，在玻璃态区的弛豫光谱的波动项增强。有人还认为，对于薄的轴对称单元的聚合物，旋转项的弛豫谱类似于稀溶液;旋转障碍沿着链的作用是相对增强的，因为从周围的旋转障碍是低的，因为该单元的对称性，因为局部应力的高波动。并通过实验验证了上述结论
Published data of dynamic birefringence and viscoelasticity of amorphous polymers were compared with the molecular expression of stress proposed by Gao and Weiner. The theory states that the stress is composed of contributions from the chain orientation (orientation term), the monomer orientation around the chain axis (rotation term), and the fluctuation of the local stress tensor (fluctuation term); the birefringence is composed of only two terms corresponding to the first two of the stress. The experimental data indicate that in the glassy zone and the high-frequency region of the glass-to-rubber transition zone the stress is attributable to the rotation and the fluctuation terms and the degrees of contribution vary with polymer species. For polymers with flat units (like polycarbonate), the fluctuation term is negligible and the relaxation spectrum in the glassy zone is low. For polymers with thin axisymmetric units (like polyisobutylene) or bulky irregular units (like poly(2-vinylnaphthalene)), the relaxation spectrum in the glassy zone is enhanced by the fluctuation term. It is also argued that, for polymers with thin axisymmetric units, the relaxation spectrum for the rotation term resembles that of a dilute solution; the role of rotational barrier along the chain is relatively enhanced since the rotational barrier from the surrounding is low because of the symmetry of the unit and because of the high fluctuation of the local stress. Some experiments are proposed to verify the statements