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Dynamic Light Scattering Studies of Polymer Chain Dynamics Under One-Dimensional Shear Flow

一维剪切流下聚合物链动力学的动态光散射研究

基本信息

批准号：
01470106
负责人：
TSUNASHIMA Yoshisuke
金额：
$ 3.01万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-01470106/
关键词：
Dynamic Light Scattering Polymer Diffusion Hydrodynamic Interaction Steady Shear Flow Oseen Tensor Navier-Stokes Equation Polymer Solution 非定常流

项目摘要

Flexible polymer chains in dilute solution show the diffusion motion due to thermal fluctuation of the chain segments. Dynamic light scattering spectroscopy has given direct information on the trans-lational diffusion coefficient and the internal relaxation times of the chains. However, the experimental results has not fully been explained from the theoretical and molecular point of view. The main reason might be due to Oseen approximation which has been customarily used to describe the hydrodynamic interaction exerted on the chain segments. It is well known that when the incompressible fluid is set in an one-dimensional flow, e. g., Couette flow, the Navier-Stokes equation describes exactly the hydrodynamics of the fluid and its exact solution gives the diffusion coefficient of suspended particles in the fluid without any approximation to the hydrodynamic interaction. In this work, We put the polymer chain into such an one-dimensional Couette flow and study the polymer chain dynamics through the dynamic light scattering technique. We poured dilute solutions of polystyrene (Mw=7.76x10^5) and poly (alphaーmethylstyrene) (Mw=2.7x10^6) in benzene (good solvent for both polymers) into the gap between an inner rotating and an outer rest cylinders of a coaxial rotating cylinder viscometer. An eddy-current drive of the inner cylinder yielded a very low shear flow intohe range of 0.57 - 5.3 sec^<-1>. The time correlation function of the scattered light from the solution was measured by a time-interval correlator and was then analyzed to estimate the translaーtional diffusion coefficient and the internal motions of the polymer chains in the Couette flow. Tt is found that the chain dynamics revealed shear-rate dependent behavior, but that at a small finite shear rate the internal motions disappeared and the translational diffusion coefficient could be detected without any ambiguity.

稀溶液中的柔性聚合物链由于链段的热波动而表现出扩散运动。动态光散射光谱提供了有关链的平移扩散系数和内部弛豫时间的直接信息。然而，实验结果尚未从理论和分子角度得到充分解释。主要原因可能是由于 Oseen 近似，该近似通常用于描述施加在链段上的流体动力相互作用。众所周知，当不可压缩流体处于一维流动时，例如。例如，库埃特流，纳维-斯托克斯方程准确地描述了流体的流体动力学，其精确解给出了流体中悬浮颗粒的扩散系数，而没有任何流体动力学相互作用的近似。在这项工作中，我们将聚合物链放入这样的一维库埃特流中，并通过动态光散射技术研究聚合物链动力学。我们将聚苯乙烯（Mw=7.76x10^5）和聚（αー甲基苯乙烯）（Mw=2.7x10^6）在苯（两种聚合物的良好溶剂）中的稀溶液倒入同轴旋转圆筒粘度计的内部旋转圆筒和外部静止圆筒之间的间隙中。内圆筒的涡流驱动产生0.57-5.3秒^ -1 范围内的非常低的剪切流。通过时间间隔相关器测量溶液散射光的时间相关函数，然后进行分析以估计平移扩散系数和库埃特流中聚合物链的内部运动。结果发现，链动力学揭示了剪切速率相关的行为，但在较小的有限剪切速率下，内部运动消失，并且可以毫无歧义地检测到平移扩散系数。