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arXiv 1409.2669cond-mat.soft
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胶体膜中手性筏的分级结构

Hierarchical organization of chiral rafts in colloidal membranes

Prerna Sharma, Andrew Ward, T. Gibaud, Michael F. Hagan, Zvonimir Dogic

摘要:

液-液相分离普遍存在于纳米颗粒、蛋白质和胶体的悬浮液中。除了少数显著的例外,在散装悬浮液中的表面张力最小化的液滴连续聚结,尺寸无限制地增加,直到实现宏观尺度的相分离。相比之下,胶体、纳米颗粒或蛋白质局限于界面、表面或膜的相行为要复杂得多。夹杂物扭曲了局部界面结构,导致与各向同性溶剂介导的充分研究的相互作用根本不同的相互作用。在这里,我们研究液-液相分离单层膜组成的不同手性胶体棒。我们证明了胶体筏是一个普遍存在的二元胶体膜的功能。我们测量筏自由能景观可视化其组装动力学。随后,我们量化排斥筏筏相互作用,并将它们直接成像筏引起的膜扭曲,表明粒子手性在这种微相分离中起着关键作用。在高密度下,筏组装成簇晶体,不断与背景水库交换单体棒,以保持自限的大小。最后,我们证明了筏可以形成键组装成更高阶的超结构。我们的工作表明,膜介导的液-液相分离可以从根本上不同于大量液体的良好表征的行为。它概述了一个强大的膜为基础的途径组装单分散液团簇,这是补充现有的方法发生在散装悬浮液。最后,它揭示了手性夹杂物在膜获得长程排斥相互作用,这可能会发挥作用,在稳定组装的有限大小。

英文摘要:

Liquid-liquid phase separation is ubiquitous in suspensions of nanoparticles, proteins and colloids. With a few notable exceptions, surface-tension-minimizing liquid droplets in bulk suspensions continuously coalesce, increasing in size without bound until achieving macroscale phase separation. In comparison, the phase behavior of colloids, nanoparticles or proteins confined to interfaces, surfaces or membranes is significantly more complex. Inclusions distort the local interface structure leading to interactions that are fundamentally different from the well-studied interactions mediated by isotropic solvents. Here, we investigate liquid-liquid phase separation in monolayer membranes composed of dissimilar chiral colloidal rods. We demonstrate that colloidal rafts are a ubiquitous feature of binary colloidal membranes. We measure the raft free energy landscape by visualizing its assembly kinetics. Subsequently, we quantify repulsive raft-raft interactions and relate them to directly imaged raft-induced membrane distortions, demonstrating that particle chirality plays a key role in this microphase separation. At high densities, rafts assemble into cluster crystals which constantly exchange monomeric rods with the background reservoir to maintain a self-limited size. Lastly, we demonstrate that rafts can form bonds to assemble into higher-order supra-structures. Our work demonstrates that membrane-mediated liquid-liquid phase separation can be fundamentally different from the well-characterized behavior of bulk liquids. It outlines a robust membrane-based pathway for assembly of monodisperse liquid clusters which is complementary to existing methods which take place in bulk suspensions. Finally, it reveals that chiral inclusions in membranes acquire long-ranged repulsive interactions, which might play a role in stabilizing assemblages of finite size.

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