Riest Jonas, Eckert Thomas, Richtering Walter, Nägele Gerhard
Forschungszentrum Jülich GmbH, ICS-3 - Soft Condensed Matter, 52428 Jülich, Germany.
Soft Matter. 2015 Apr 14;11(14):2821-43. doi: 10.1039/c4sm02816c.
We present an easy-to-use analytic toolbox for the calculation of short-time transport properties of concentrated suspensions of spherical colloidal particles with internal hydrodynamic structure, and direct interactions described by a hard-core or soft Hertz pair potential. The considered dynamic properties include self-diffusion and sedimentation coefficients, the wavenumber-dependent diffusion function determined in dynamic scattering experiments, and the high-frequency shear viscosity. The toolbox is based on the hydrodynamic radius model (HRM) wherein the internal particle structure is mapped on a hydrodynamic radius parameter for unchanged direct interactions, and on an existing simulation data base for solvent-permeable and spherical annulus particles. Useful scaling relations for the diffusion function and self-diffusion coefficient, known to be valid for hard-core interaction, are shown to apply also for soft pair potentials. We further discuss extensions of the toolbox to long-time transport properties including the low-shear zero-frequency viscosity and the long-time self-diffusion coefficient. The versatility of the toolbox is demonstrated by the analysis of a previous light scattering study of suspensions of non-ionic PNiPAM microgels [Eckert et al., J. Chem. Phys., 2008, 129, 124902] in which a detailed theoretical analysis of the dynamic data was left as an open task. By the comparison with Hertz potential based calculations, we show that the experimental data are consistently and accurately described using the Verlet-Weis corrected Percus-Yevick structure factor as input, and for a solvent penetration length equal to three percent of the excluded volume radius. This small amount of solvent permeability of the microgel particles has a significant dynamic effect at larger concentrations.
我们提出了一个易于使用的分析工具箱，用于计算具有内部流体动力学结构的球形胶体颗粒浓悬浮液的短时间传输性质，以及由硬核或软赫兹对势描述的直接相互作用。所考虑的动态性质包括自扩散系数和沉降系数、在动态散射实验中确定的波数依赖扩散函数以及高频剪切粘度。该工具箱基于流体动力学半径模型（HRM），其中内部颗粒结构被映射到一个流体动力学半径参数上，以保持直接相互作用不变，并基于现有的溶剂可渗透球形环空颗粒模拟数据库。已知对硬核相互作用有效的扩散函数和自扩散系数的有用标度关系，也被证明适用于软对势。我们进一步讨论了将工具箱扩展到长时间传输性质，包括低剪切零频率粘度和长时间自扩散系数。通过对先前关于非离子型PNiPAM微凝胶悬浮液的光散射研究[Eckert等人，《化学物理杂志》，2008年，129卷，124902]的分析，证明了该工具箱的通用性，其中对动态数据的详细理论分析仍是一个未完成的任务。通过与基于赫兹势的计算结果进行比较，我们表明，使用Verlet-Weis校正的Percus-Yevick结构因子作为输入，并且对于溶剂渗透长度等于排除体积半径的3%，实验数据能够得到一致且准确的描述。微凝胶颗粒这种少量的溶剂渗透性在较高浓度下具有显著的动态效应。
