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arXiv 1012.3605cond-mat.softcond-mat.stat-mech
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具有不同斑块数的斑块状胶体二元混合物的Phase diagrams:网络流体状态

Phase diagrams of binary mixtures of patchy colloids with distinct numbers of patches: The network fluid regime

Daniel de las Heras, José M. Tavares, Margarida M. Telo da Gama

摘要:

我们计算的网络流体制度和二元混合物的斑块状胶体的相图,使用Wertheim的一阶微扰理论和Flory-Stockmayer的聚合理论的推广。胶体被建模为具有相同直径和相同类型的表面贴片的硬球,$A$。物种之间的唯一区别是其补丁的数量-或功能-$f_A^{(1)}$和$f_A^{(2)}$(与$f_A^{(2)}>f_A^{(1)}$)。我们已经发现,在功能的差异是控制的行为的混合物在网络(膨胀)流体制度的关键因素。特别地,当$f_A^{(2)}\ge2f_A^{(1)}$时,键合熵驱动两种网络流体的相分离,这在其他混合物中不存在。当$f_A^{(1)}>2$时,这会极大地改变系统的临界特性,并驱动相图拓扑结构的变化(从I型到V型)。官能度的差异也决定了在高(渗透)压下的溶解性。如果是$f_A^{(2)}-f_A^{(1)}=1$,则混合物在高压下是完全混溶的,而如果是$f_A^{(2)}-f_A^{(1)}>1$,则在高于纯流体的最高临界压力的压力下存在闭合的混溶间隙。我们认为,这种相行为是由混合的熵和结合的熵之间的竞争,后者占主导地位的网络流体制度。

英文摘要:

We calculate the network fluid regime and phase diagrams of binary mixtures of patchy colloids, using Wertheim's first order perturbation theory and a generalization of Flory-Stockmayer's theory of polymerization. The colloids are modelled as hard spheres with the same diameter and surface patches of the same type, $A$. The only difference between species is the number of their patches -or functionality-, $f_A^{(1)}$ and $f_A^{(2)}$ (with $f_A^{(2)}>f_A^{(1)}$). We have found that the difference in functionality is the key factor controlling the behaviour of the mixture in the network (percolated) fluid regime. In particular, when $f_A^{(2)}\ge2f_A^{(1)}$ the entropy of bonding drives the phase separation of two network fluids which is absent in other mixtures. This changes drastically the critical properties of the system and drives a change in the topology of the phase diagram (from type I to type V) when $f_A^{(1)}>2$. The difference in functionality also determines the miscibility at high (osmotic) pressures. If $f_A^{(2)}-f_A^{(1)}=1$ the mixture is completely miscible at high pressures, while closed miscibility gaps at pressures above the highest critical pressure of the pure fluids are present if $f_A^{(2)}-f_A^{(1)}>1$. We argue that this phase behaviour is driven by a competition between the entropy of mixing and the entropy of bonding, as the latter dominates in the network fluid regime.

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