Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA.
J Chem Phys. 2011 Dec 21;135(23):234902. doi: 10.1063/1.3669649.
The relationship between kinetic arrest, connectivity percolation, structure and phase separation in protein, nanoparticle, and colloidal suspensions is a rich and complex problem. Using a combination of integral equation theory, connectivity percolation methods, naïve mode coupling theory, and the activated dynamics nonlinear Langevin equation approach, we study this problem for isotropic one-component fluids of spheres and variable aspect ratio rigid rods, and also percolation in rod-sphere mixtures. The key control parameters are interparticle attraction strength and its (short) spatial range, total packing fraction, and mixture composition. For spherical particles, formation of a homogeneous one-phase kinetically stable and percolated physical gel is predicted to be possible, but depends on non-universal factors. On the other hand, the dynamic crossover to activated dynamics and physical bond formation, which signals discrete cluster formation below the percolation threshold, almost always occurs in the one phase region. Rods more easily gel in the homogeneous isotropic regime, but whether a percolation or kinetic arrest boundary is reached first upon increasing interparticle attraction depends sensitively on packing fraction, rod aspect ratio and attraction range. Overall, the connectivity percolation threshold is much more sensitive to attraction range than either the kinetic arrest or phase separation boundaries. Our results appear to be qualitatively consistent with recent experiments on polymer-colloid depletion systems and brush mediated attractive nanoparticle suspensions.
蛋白质、纳米粒子和胶体悬浮液中动力学停滞、连通性逾渗、结构和相分离之间的关系是一个丰富而复杂的问题。我们使用积分方程理论、连通性逾渗方法、朴素模式耦合理论和激活动力学非线性朗之万方程方法，研究了各向同性单组分球体和可变纵横比刚性棒的流体，以及棒-球混合物中的逾渗问题。关键控制参数是粒子间吸引力强度及其（短程）空间范围、总堆积分数和混合物组成。对于球形粒子，预测形成均匀单相动力学稳定且逾渗的物理凝胶是可能的，但取决于非普适因素。另一方面，向激活动力学和物理键形成的动态转变，标志着在逾渗阈值以下离散团簇的形成，几乎总是发生在单相区域。棒状粒子在均匀各向同性态下更容易凝胶，但在增加粒子间吸引力时，首先达到逾渗或动力学停滞边界取决于堆积分数、棒状纵横比和吸引力范围。总体而言，连通性逾渗阈值对吸引力范围的敏感性远高于动力学停滞或相分离边界。我们的结果似乎与最近关于聚合物-胶体耗散系统和刷介导的吸引力纳米粒子悬浮液的实验定性一致。
