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首页> 外文期刊>The Journal of Chemical Physics >Effective electrostatic interactions in solutions of polyelectrolyte stars with rigid rodlike arms
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Effective electrostatic interactions in solutions of polyelectrolyte stars with rigid rodlike arms

机译：具有刚性杆状臂的聚电解质恒星溶液中的有效静电相互作用

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摘要

In solutions of star-branched polyelectrolytes, electrostatic interactions between charged arms on neighboring stars can compete with intrastar interactions and rotational entropy to induce anisotropy in the orientational distribution of arms. We explore the influence of arm orientational anisotropy on effective star-star interactions for model stars comprising rigid rodlike arms with evenly spaced charged monomers interacting via an effective screened-Coulomb (Yukawa) potential. Monte Carlo simulation and density-functional theory are used to compute the arm orientational distributions and effective pair potentials between weakly charged stars. For comparison, a torque balance analysis is performed to obtain the configuration and energy of the ground state, in which the torque vanishes on each arm of the two-star system. The degree of anisotropy is found to increase with the strength of electrostatic interactions and proximity of the stars. As two stars begin to overlap, the forward arms are pushed back by interstar arm-arm repulsion, but partially interdigitate due to rotational entropy. At center-center separations approaching complete overlap, the arms relax to an isotropic distribution. For nonoverlapping stars, anisotropy-induced changes in the intra- and interstar arm-arm interactions largely cancel and the effective pair interactions are then well approximated by a simple Yukawa potential, as predicted by linear-response theory for a continuum model of isotropic stars [A. R. Denton, Phys. Rev. E 67, 11804 (2003)]. For overlapping stars, the effective pair interactions in the simple rigid-arm-Yukawa model agree closely with simulations of a molecular model that includes flexible arms and explicit counterions [A. Jusufi , Phys. Rev. Lett. 88, 018301 (2002); J. Chem. Phys. 116, 11011 (2002)]. (c) 2005 American Institute of Physics.
机译：在星形支化的聚电解质溶液中，相邻恒星上带电臂之间的静电相互作用可以与恒星内相互作用和旋转熵竞争，从而在臂的定向分布中引起各向异性。我们探索了臂向各向异性对模型恒星有效星-星相互作用的影响，该模型恒星包括刚性杆状臂和均匀间隔的带电单体，通过有效的筛选库仑（Yukawa）势相互作用。蒙特卡罗模拟和密度泛函理论用于计算微弱带电恒星之间的臂取向分布和有效对势。为了比较，执行扭矩平衡分析以获得基态的构造和能量，其中扭矩在双星系统的每个臂上消失。发现各向异性程度随着静电相互作用的强度和恒星的接近而增加。当两颗恒星开始重叠时，前臂由于星际臂－臂的排斥而向后推，但由于旋转熵而部分地相互交叉。在中心-中心间距接近完全重叠的情况下，臂会松弛成各向同性的分布。对于非重叠恒星，各向异性引起的星内和星际手臂间相互作用的变化基本抵消，然后通过简单的汤川势很好地近似有效的对相互作用，如线性响应理论所预测的各向同性恒星连续模型[一种。 R. Denton，物理学E 67，11804（2003）。对于重叠的恒星，简单的刚性臂-汤川模型中的有效对相互作用与包含柔性臂和显性抗衡离子的分子模型的模拟非常吻合[A. Jusufi，物理学。牧师88，018301（2002）; J.化学物理116，11011（2002）]。 （c）2005年美国物理研究所。

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