Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Soft Matter. 2018 Oct 31;14(42):8570-8579. doi: 10.1039/c8sm01678j.
Recent studies of colloidal systems with a short-range attraction and long-range repulsion (SALR) have been demonstrated to have a generalized phase diagram with multiple liquid states defined by their structures. In this paper, we identify the different liquid states of previous experimentally studied lysozyme samples within this proposed generalized state diagram and explore the dynamic properties of each liquid state. We show that most lysozyme samples studied here and previously at low and intermediate concentrations are dispersed fluids while a few high concentration samples are randomly percolated liquids. In the dispersed fluid region, the short-time diffusion coefficient measured by neutron spin echo agrees well with the long time diffusion coefficient estimated with the solution viscosity. This dynamic feature is maintained even for some samples in the random percolated region. However, the short-time and long-time diffusion coefficients of random percolated fluids deviate at larger concentration and attraction strength. At high enough concentrations, the mean square displacement can be as slow as those of many glassy colloidal systems at time scales near the characteristic diffusion time even though these lysozyme samples remain in liquid states at the long-time limit. We thus identify the region in the generalized phase diagram where these equilibrium states with extremely slow local dynamics exist relative to bulk percolation and kinetic arrest (gel and glassy) transitions.
最近对具有短程吸引力和长程排斥力（SALR）的胶体系统的研究表明，具有由其结构定义的多个液相的广义相图。在本文中，我们在提出的广义状态图中确定了先前在实验中研究的溶菌酶样品的不同液相，并探索了每个液相的动态特性。我们表明，此处和先前在低浓度和中等浓度下研究的大多数溶菌酶样品都是分散的流体，而少数高浓度的样品则是随机渗透的液体。在分散的流体区域中，通过中子自旋回波测量的短时间扩散系数与通过溶液粘度估计的长时间扩散系数吻合得很好。即使在随机渗透区域的某些样品中，这种动态特征也得以保持。然而，随机渗透流体的短时间和长时间扩散系数在较大浓度和吸引力强度下会偏离。在足够高的浓度下，均方位移可以像许多玻璃状胶体系统在接近特征扩散时间的时间尺度上一样缓慢，即使这些溶菌酶样品在长时间限制下仍处于液相。因此，我们确定了在广义相图中，相对于整体渗透和动力学阻滞（凝胶和玻璃态）转变，这些具有极慢局部动力学的平衡状态存在的区域。
