Marshall Bennett D, Chapman Walter G
Department of Chemical and Biomolecular Engineering, Rice University, 6100 S. Main, Houston, Texas 77005, USA.
Soft Matter. 2014 Jul 28;10(28):5168-76. doi: 10.1039/c4sm00586d.
In this work we extend Wertheim's thermodynamic perturbation theory (TPT) to binary mixtures (species A and species B) of patchy colloids were each species has a single patch which can bond a maximum of twice (divalent). Colloids are treated as hard spheres with a directional conical association site. We restrict the system such that only patches between unlike species share attractions; meaning there are AB attractions but no AA or BB attractions. The theory is derived in Wertheim's two density formalism for one site associating fluids. Since the patches are doubly bondable, associated chains, of all chain lengths, as well as 4-mer rings consisting of two species A and two species B colloids are accounted for. With the restriction of only AB attractions, triatomic rings of doubly bonded colloids, which dominate in the corresponding pure component case, cannot form. The theory is shown to be in good agreement with Monte Carlo simulation data for the structure and thermodynamics of these patchy colloid mixtures as a function of temperature, density, patch size and composition. It is shown that 4-mer rings dominate at low temperature, inhibiting the polymerization of the mixture into long chains. Mixtures of this type have been recently synthesized by researchers. This work provides the first theory capable of accurately modeling these mixtures.
在这项工作中，我们将韦特海姆的热力学微扰理论（TPT）扩展到了斑状胶体的二元混合物（A物种和B物种），其中每个物种都有一个单一的斑块，最多可形成两次键合（二价）。胶体被视为具有定向锥形缔合位点的硬球。我们对系统进行了限制，使得只有不同物种之间的斑块存在吸引力；这意味着存在AB吸引力，但不存在AA或BB吸引力。该理论是在韦特海姆针对单位点缔合流体的双密度形式体系中推导出来的。由于斑块可形成双键，所以考虑了所有链长的缔合链以及由两个A物种和两个B物种胶体组成的四聚体环。由于仅存在AB吸引力的限制，在相应纯组分情况下占主导的双键合胶体的三原子环无法形成。结果表明，该理论与这些斑状胶体混合物的结构和热力学的蒙特卡罗模拟数据在温度、密度、斑块大小和组成的函数关系上吻合良好。结果表明，四聚体环在低温下占主导，抑制了混合物聚合成长链。这类混合物最近已由研究人员合成。这项工作提供了首个能够准确模拟这些混合物的理论。
