Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.
J Chem Phys. 2018 Jan 14;148(2):024307. doi: 10.1063/1.5011989.
We study the spatial distribution of conformational isomers surrounding a central macroion in a charged droplet with linear dimensions in the nanometer range. Dimethyl carbonate and formic acid are selected as typical solvents that undergo isomerization and a charged buckyball (C) is selected as a representative example of a macroion. The study is performed by atomistic molecular dynamics simulations. We find that when the charge of the buckyball is above a threshold value, it induces the formation of concentric shells of different conformational isomers surrounding the macroion. The presence of layers with different dielectric properties necessitates the use of different state equations for the solvent polarization in each layer. We find that at a high charge state of the buckyball, the nearest layer to the macroion comprises the conformers with the highest dipole moment. The interface of the outer layers of conformers is characterized by "ray"-forming structures of the higher dielectric constant isomers penetrating into the layer of the lowest dielectric constant isomers. For high values of the solvent dielectric constant, the charged droplet acquires a "star"-like global shape. We demonstrate that these distinct droplet structures are a manifestation of charge-induced instability. We describe this simulation-based phenomenology by an analytical theory that supports this conclusion. The findings suggest new experimental research venues that may explore the reactivity and assembly of molecules within regions of different dielectric properties in droplets.
我们研究了在纳米尺寸范围内的带电荷液滴中，围绕中心大分子的构象异构体的空间分布。我们选择了碳酸二甲酯和甲酸作为典型的溶剂，它们会发生异构化，而富勒烯（C）被选为大分子的代表性例子。这项研究是通过原子分子动力学模拟进行的。我们发现，当富勒烯的电荷超过一个阈值时，它会诱导围绕大分子形成不同构象异构体的同心壳层。不同介电性能的层的存在需要为每个层中的溶剂极化使用不同的状态方程。我们发现，在富勒烯的高电荷状态下，最靠近大分子的层包含具有最高偶极矩的构象。构象的外层界面的特征是具有较高介电常数的异构体的“射线”形成结构穿透到具有较低介电常数的异构体层中。对于较高的溶剂介电常数，带电荷的液滴会获得“星”状的全局形状。我们证明了这些独特的液滴结构是电荷诱导不稳定性的表现。我们通过支持这一结论的分析理论来描述这种基于模拟的现象学。这些发现为探索分子在液滴中不同介电性质区域内的反应性和组装提供了新的实验研究途径。
