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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 et al.,Phys.Rev.Lett.88,018301 (2002);J.Chem.Phys.116,11011 (2002)].
机译：在星形支化聚电解质溶液中，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，从而在臂的取向分布中引起各向异性。我们研究了臂取向各向异性对模型中有效星-星相互作用的影响由刚性杆状臂组成的恒星，通过有效的屏蔽库仑（Yukawa）势相互作用，带有均匀分布的带电单体。“蒙特卡罗模拟”和密度泛函理论用于计算弱带电恒星之间的臂取向分布和有效对势。然后，进行扭矩平衡分析以获得基态的构型和能量，其中两星系统各臂上的扭矩消失。发现各向异性程度随静电相互作用的强度和接近度的增加而增加。星星。随着两颗星星开始重叠，前臂由星际臂间排斥力推回，但由于旋转熵而部分交指。在中心-中心间隔接近完全重叠时，两臂松弛成各向同性分布。对于不重叠的恒星，各向异性引起星内和星际臂的变化。如线性响应理论所预测的各向同性恒星的连续模型，臂相互作用在很大程度上抵消了，然后有效的对相互作用被简单的Yukawa势很好地近似了[ARDenton，Phys.Rev.E 67,11804（2003）]。对于重叠的恒星，简单的刚性臂Yukawa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等人，Phys.Rev.Lett.88,018301（ 2002）; J.Chem.Phys.116,11011（2002）]。

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