Department of NanoEngineering, 9500 Gilman Drive, Mail Code 0448, University of California, San Diego, La Jolla, California 92093, USA.
J Phys Chem B. 2010 Dec 9;114(48):15886-96. doi: 10.1021/jp1029085. Epub 2010 Nov 11.
We report here the effects of chain stiffness and surface attachment on the effective interactions between polyelectrolyte-grafted colloidal particles in monovalent salt obtained using Monte Carlo simulations. Our approach involves computation of the distance-dependent potential of mean force between two polyelectrolyte-grafted colloidal particles treated at a coarse-grained resolution. Two chain stiffnesses, flexible and stiff, and two surface attachment modes, free and constrained, at low grafting densities are examined. PMF calculations across a range of surface and polyelectrolyte charge allows us to map out the strength and extent of the attractive and repulsive regime in the two-dimensional charge space. We observe striking differences in the effects of chain stiffness between the two modes of attachment. When the chains are freely attached, the stiff-chains colloids exhibit a marginal reduction in the attraction compared to their flexible-chain counterparts. In contrast, when the chains are attached in a constrained manner, the colloids with stiff chains exhibit a significantly stronger attraction and a broader attractive regime compared to flexible-chain colloids. These differences in the effects of stiffness between the two attachment modes are explained in terms of differences in the energetic and entropic forces balancing adsorption of chains at their own surface versus chain extension to mediate bridging interactions across two particles. Our results thus underscore the importance of surface attachment of chains and its proper accounting in computational and experimental studies and suggests the mode of chain attachment as an additional control parameter for modulating intercolloid interactions for applications such as stabilization of colloidal systems and bottom-up self-assembly of nanostructures.
我们在这里报告了在单盐中使用蒙特卡罗模拟研究链刚性和表面附着对聚电解质接枝胶体粒子之间有效相互作用的影响。我们的方法涉及计算在粗粒度分辨率下处理的两个聚电解质接枝胶体粒子之间的距离相关平均力势能。研究了两种链刚性，柔性和刚性，以及两种表面附着模式，低接枝密度下的自由和约束。PMF 计算跨越一系列表面和聚电解质电荷，使我们能够在二维电荷空间中描绘出吸引和排斥区域的强度和范围。我们观察到两种附着模式之间链刚性的影响有显著差异。当链自由附着时，与柔性链胶体相比，刚性链胶体的吸引力略有降低。相比之下，当链以约束方式附着时，与柔性链胶体相比，刚性链胶体表现出更强的吸引力和更宽的吸引区域。两种附着模式之间刚度影响的差异可以用链在自身表面上吸附的能量和熵力与链延伸以介导两个粒子之间的桥接相互作用的平衡来解释。我们的结果因此强调了链的表面附着及其在计算和实验研究中的正确考虑的重要性，并提出了链附着模式作为调节胶体间相互作用的附加控制参数，例如胶体系统的稳定化和自下而上的纳米结构组装。
