Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, CH-1700 Fribourg, Switzerland.
Division of Physical Chemistry, Department of Chemistry, Lund University, Naturvetarvägen 16, SE-223 62 Lund, Sweden.
Soft Matter. 2018 May 16;14(19):3704-3715. doi: 10.1039/C8SM00160J.
Short-range attractive colloids show well-defined phase behaviour in the absence of repulsions, and highly intriguing equilibrium gelation in the presence of long-range repulsions. We present the state diagram of short-range attractive colloids with repulsions that range from fully screened to intermediately ranged, i.e. longer-ranged than the attractions, but shorter ranged than the colloid size. We demonstrate that although the macroscopic phase behaviour does not change perceptibly, there is a dramatic increase of inhomogeneities once the repulsions become longer-ranged than the attractions. The interaction potentials are characterized with small angle neutron scattering, and used to renormalize the state diagram with the minimum in the interaction potential, min[U(r)], and with the reduced second virial coefficient, B2*. We find that the extended law of corresponding states captures the onset of phase separation for shorter ranged repulsions, but fails for longer ranged repulsions. Instead, for a given model of U(r), the transition from visually homogeneous fluid to phase separation and/or gelation can be rescaled with min[U(r)] over the full range of repulsions. Finally, we suggest a generic state diagram to describe the effect of repulsions on short-range attractive systems.
短程吸引力胶体在没有排斥力的情况下表现出明确的相行为，而在存在长程排斥力的情况下则表现出非常有趣的平衡凝胶化。我们呈现了具有排斥力的短程吸引力胶体的状态图，排斥力范围从完全屏蔽到中等范围，即比吸引力范围更长，但比胶体尺寸更短。我们证明，尽管宏观相行为没有明显变化，但一旦排斥力变得比吸引力范围更长，不均匀性就会急剧增加。用小角度中子散射对相互作用势进行了表征，并用于用相互作用势的最小值 min[U(r)]和有效第二维里系数 B2*来重新归一化状态图。我们发现，扩展的对应状态定律可以捕捉到较短程排斥力下相分离的开始，但对于较长程排斥力则不行。相反，对于给定的 U(r)模型，从视觉上均匀的流体到相分离和/或凝胶化的转变可以通过 min[U(r)]在整个排斥力范围内进行缩放。最后，我们提出了一个通用的状态图来描述排斥力对短程吸引力系统的影响。
