凝胶中动态光散射强度的测量
Measurement of Dynamic Light Scattering Intensity in Gels
摘要：
在科学文献中，很少有人注意到使用动态光散射（DLS）作为提取凝胶散射光的绝对强度中包含的热力学信息的工具。在这篇文章中，我们表明，DLS产生可靠的测量光散射的热力学波动的强度，不仅在聚合物水溶液中，而且在水凝胶。在水凝胶中，由渗透波动散射的光被来自静态或缓慢变化的不均匀性的光外差。这两个组成部分是可分离的，由于其不同的时间尺度，给出了良好的实验协议与宏观测量的渗透压。然而，凝胶中的DLS测量是从网络中去偏振光散射以及多重光散射的支流。本文探讨了这些影响，以及所需的仪器校正，以确定渗透模量。对于被困在水凝胶中的客体聚合物，外推到零浓度的测量强度与通过溶液中相同聚合物的静态光散射发现的强度相同。凝胶环境改变了第二维里系数和第三维里系数，提供了一种评价聚合物和凝胶之间相互作用的方法。
英文摘要：
In the scientific literature little attention has been given to the use of dynamic light scattering (DLS) as a tool for extracting the thermodynamic information contained in the absolute intensity of light scattered by gels. In this article we show that DLS yields reliable measurements of the intensity of light scattered by the thermodynamic fluctuations, not only in aqueous polymer solutions, but also in hydrogels. In hydrogels, light scattered by osmotic fluctuations is heterodyned by that from static or slowly varying inhomogeneities. The two components are separable owing to their different time scales, giving good experimental agreement with macroscopic measurements of the osmotic pressure. DLS measurements in gels are, however, tributary to depolarised light scattering from the network as well as to multiple light scattering. The paper examines these effects, as well as the instrumental corrections required to determine the osmotic modulus. For guest polymers trapped in a hydrogel the measured intensity, extrapolated to zero concentration, is identical to that found by static light scattering from the same polymers in solution. The gel environment modifies the second and third virial coefficients, providing a means of evaluating the interaction between the polymers and the gel.
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