Dynamic Light Scattering Investigations of Segmental Motion and Viscoelasticity in Polymers

这项关于聚合物中局部链段运动动力学的研究将包括半稀释区和浓度区以及可混溶聚合物混合物中的聚合物溶液。要使用的技术是各种类型的动态光散射，包括光子相关光谱、布里渊散射和全息光栅弛豫。研究了标记链在半稀或/和浓聚合物溶液中的动态纵向和剪切柔度、动态纵向和剪切弹性系数、超音速和衰减系数、互扩散系数和示踪扩散系数等性质。光谱将作为聚合物相对分子质量、浓度、散射波矢和溶剂质量的函数进行测量。将努力将动态光散射与聚合物溶液的机械弛豫谱联系起来。理论预测的实验验证是本研究的一部分。还将通过静态和动态光散射强度测量来研究可相容聚合物共混物中的动力学和热力学相互作用。通过结合聚合物共混物的互扩散系数和自扩散系数的结果，将澄清同一链的链段之间和相邻链之间的交叉速度关联的作用。互扩散系数可用光子相关光谱仪测量，自扩散系数可用脉冲场梯度Nm或全息栅弛豫技术测量。了解聚合物的热力学相互作用和局部链段运动的动力学对于聚合物在涂料、电子、光学和结构材料等不同领域的各种应用至关重要。

This study of the dynamics of local segmental motion in polymers will include polymer solutions in semi-dilute and concentrated regions and in miscible polymer blends. The techniques to be used are various types of dynamic light scattering, including photon correlation spectroscopy, Brillouin scattering and holographic grating relaxation. Properties such as dynamic longitudinal and shear compliances, dynamic longitudinal and shear moduli, hyper- sonic velocity and attenuation coefficient, mutual and tracer diffusion coefficients of labeled chains in the semi-dilute or/and concentrated polymer solutions will be investigated. The spectrum will be measured as a function of polymer molecular weight, concentration, scattering wavevector, and solvent qualities. Efforts will be made to relate the dynamic light scattering to the mechanical relaxation spectrum of the polymer solution. Experi- mental verification of theoretical predictions is part of this research. The kinetics and thermodynamics interaction in miscible polymer blends will also be investigated by the static and dynamic light scattering intensity measurements. By combining the results of mutual and self-diffusion coefficients of the polymer blend, the role of cross velocity correlations between segments of the same chain and between neighboring chains will be clarified. The mutual diffusion coefficient will be measured by using photon correlation spectroscopy, the self diffusion coefficient by pulsed field gradient NM or by the holographic grating relaxation tech- nique whenever appropriate. Understanding of the thermodynamic interactions and the dynamics of local segmental motion is vital to various application of polymers in diverse areas, such as coatings, electronics, optics, and structural materials.