DIFFUSION AND INTERACTION IN GELS AND SOLUTIONS .3. THEORETICAL RESULTS ON THE OBSTRUCTION EFFECT
DIFFUSION AND INTERACTION IN GELS AND SOLUTIONS .3. THEORETICAL RESULTS ON THE OBSTRUCTION EFFECT
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DOI：
10.1021/ma00022a019
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发表时间：
1991-10-28
期刊：
影响因子：
5.5
通讯作者：
LOFROTH, JE
中科院分区：
文献类型：
--
作者：
JOHANSSON, L;ELVINGSON, C;LOFROTH, JE
提出了一种球形溶质在聚合物凝胶或溶液网络中扩散的新理论。该网络中的空间分布被用来评估一个频率函数，该频率函数给出了不同半径的柱状单元的权重。一旦频率函数已知，有效扩散系数就可以用数值或解析的方法从圆柱体模型中由Fick第一定律的解给出的局部扩散系数计算出来。将预测结果与布朗动力学模拟、文献数据和我们自己的实验结果进行了比较。结果表明，该理论能很好地预测溶质在柔性和刚性聚合物体系中的扩散。一个结果是，溶质在柔性聚合物体系中的扩散比在刚性聚合物体系中的扩散更快。一个重要的参数是比率p/a，其中p是聚合物的持续长度，a是它的半径。结果表明，Ogston给出的空间分布可以用来定性地描述p/a>；10时的势垒，而在这种情况下，也可以用所给出的解析理论进行定量预测。当p/a<；10时，可以进行溶质扩散的数值计算。因此，本文的方法导致了一个具有广泛应用范围的理论。
A new theory for the diffusion of a spherical solute in a network, e.g., a polymer gel or solution, is presented. The distribution of spaces in the network is used to evaluate a frequency function giving the weights of cylindrical cells with different radii. Once the frequency function is known, the effective diffusion coefficient can be calculated, numerically or analytically, from the local diffusion coefficients given by the solution of Fick's first law in the cylindrical cell model. The predictions are compared with Brownian dynamics simulations, literature data, and results from our own experiments. It is found that the theory can successfully predict the diffusion of solutes in both flexible and stiff polymer systems. One result is that the diffusion of a solute is faster in a system of flexible polymers than in a system of stiff polymers. A crucial parameter is the ratio p/a, where p is the persistence length of the polymer and a is its radius. It is shown that the space distribution given by Ogston can be used to give a qualitative description of the hindrance when p/a > 10. However, in this case a quantitative prediction can also be made by the analytical theory presented here. When p/a < 10, a numerical calculation of the solute diffusion can be carried out. Thus, the approach in this paper leads to a theory with a wide range of applications.