Center for Theoretical Physics and Key Laboratory of Artificial Micro and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, China.
College of Electrical and Photoelectronic Engineering, West Anhui University, Lu'an 237012, China.
J Chem Phys. 2019 Sep 21;151(11):114902. doi: 10.1063/1.5120756.
Ion-mediated interactions are very important for the properties of colloids and biomacromolecules such as nucleic acids and proteins. In this work, the ion-mediated interactions between equally and oppositely charged spherical polyelectrolytes (SPEs) in symmetrical divalent electrolytes have been investigated by Monte Carlo simulations, and an unexpected apparent repulsion was observed at high divalent salt concentration. Our investigations also show that the effective repulsion becomes more pronounced for SPEs with higher charge densities and for counterions with larger sizes and was found to be tightly accompanied with the over-neutralization to SPEs by condensed counterions and their release upon the approach of SPEs. Such attractive interaction can be reproduced by our proposed modified Poisson-Boltzmann model and is mainly attributed to the increase in the electrostatic repulsion between on charged SPE and the over-neutralized counterions around the other oppositely SPE with the approach of the two SPEs.
离子介导的相互作用对于胶体和生物大分子（如核酸和蛋白质）的性质非常重要。在这项工作中，通过蒙特卡罗模拟研究了等电和反电荷的球形聚电解质（SPE）在对称二价电解质中的离子介导相互作用，在高二价盐浓度下观察到了出乎意料的明显排斥。我们的研究还表明，对于具有更高电荷密度的 SPE 和具有更大尺寸的抗衡离子，有效排斥变得更加明显，并且发现它与凝聚抗衡离子对 SPE 的过中和以及 SPE 接近时它们的释放紧密相关。这种吸引力可以通过我们提出的改进的泊松-玻尔兹曼模型来重现，主要归因于随着两个 SPE 的接近，带电荷的 SPE 之间的静电排斥增加，以及另一个 SPE 周围的过中和抗衡离子。
