Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540, USA.
J Chem Phys. 2013 Jul 14;139(2):024907. doi: 10.1063/1.4811393.
We investigate the depletion-induced phase behavior of athermal colloid-star polymer mixtures on a fine lattice using grand canonical Monte Carlo simulations in the "protein limit," that is, where polymer dimensions exceed those of the colloid. We consider the influence of the star's functionality, f, the macroscopic size ratio, qr = 2Rg, s∕σc, where Rg, s is the radius of gyration of the star and σc is the colloid diameter, and the microscopic size ratio, d = σm∕σc, where σm is the diameter of a Kuhn segment. Recent theoretical predictions concerning the qualitative interplay of qr and f in determining the phase stability of these mixtures [D. Marzi, C. N. Likos, and B. Capone, J. Chem. Phys. 137, 014902 (2012)] in the limit of large f are mostly corroborated by our results which span a much lower range of functionalities. Our results suggest a direct connection between the phase behavior and the scaling regimes of single star structure in the classical Daoud-Cotton (DC) description [M. Daoud and J. P. Cotton, J. Phys. 43, 531-538 (1982)]. Using this formalism, we define a "low" functionality limit through scaling arguments, for which our model provides a mapping of the phase behavior of colloidal mixtures with star polymers (f > 2) to linear chains (f = 2). Furthermore, our simulations suggest that as qr increases, both the critical monomer and colloid densities tend to a constant, finite value for all f; thus, we do not find the prediction by Marzi and co-workers of an upper limit to immiscibility (infinite critical densities) in terms of qr to be accurate for the stars we have investigated.
我们使用巨正则蒙特卡罗模拟在“蛋白质极限”下研究了非热胶体-星聚合物混合物在精细晶格上的耗尽诱导相行为，即在聚合物尺寸超过胶体尺寸的情况下。我们考虑了星的功能，f，宏观尺寸比，qr = 2Rg，s∕σc，其中 Rg，s 是星的回转半径，σc 是胶体直径，和微观尺寸比，d = σm∕σc，其中 σm 是 Kuhn 段的直径。最近的理论预测了这些混合物的相稳定性的定性相互作用，涉及 qr 和 f 在大量 f 极限下的相互作用[D. Marzi，C. N. Likos 和 B. Capone，J. Chem. Phys. 137，014902（2012）]，我们的结果大部分得到了证实，我们的结果跨越了一个功能范围小得多的范围。我们的结果表明，相行为和在经典 Daoud-Cotton（DC）描述[M. Daoud 和 J. P. Cotton，J. Phys. 43，531-538（1982）]中单星结构的标度区之间存在直接联系。使用这种形式主义，我们通过标度论证定义了一个“低”功能范围，对于这个范围，我们的模型提供了胶体混合物与星形聚合物（f > 2）的相行为的映射到线性链（f = 2）。此外，我们的模拟表明，随着 qr 的增加，对于所有 f，临界单体和胶体密度都趋于一个常数，有限值；因此，我们没有发现 Marzi 及其同事的预测，即 qr 方面的不混溶性（无限临界密度）的上限对于我们研究的星是准确的。
