Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK..
Molecules. 2019 Feb 9;24(3):608. doi: 10.3390/molecules24030608.
We report on molecular simulations of model fluids composed of three tangentially bonded Lennard-Jones interaction sites with three distinct morphologies: a flexible "pearl-necklace" chain, a rigid "stiff" linear configuration, and an equilateral rigid triangular ring. The adsorption of these three models in cylindrical pores of diameters 1, 2, and 3 nm and with varying solid⁻fluid strength was determined by direct molecular dynamics simulations, where a sample pore was placed in contact with a bulk fluid. Adsorption isotherms of Type I, V, and H1 were obtained depending on the choice of pore size and solid⁻fluid strength. Additionally, the bulk-phase equilibria, the nematic order parameter of the adsorbed phase, and the self-diffusion coefficient in the direction of the pore axis were examined. It was found that both the molecular shape and the surface attractions play a decisive role in the shape of the adsorption isotherm. In general, the ring molecules showed a larger adsorption, while the fully flexible model showed the smallest adsorption. Morphology and surface strength were found to have a lesser effect on the diffusion of the molecules. An exceptional high adsorption and diffusion, suggesting an enhanced permeability, was observed for the linear stiff molecules in ultraconfinement, which was ascribed to a phase transition of the adsorbed fluid into a nematic liquid crystal.
我们报告了由三个具有三种不同形态的切向键合 Lennard-Jones 相互作用位点组成的模型流体的分子模拟：柔性“珍珠项链”链、刚性“硬”线性构型和等边刚性三角形环。通过直接分子动力学模拟确定了这些模型在直径为 1、2 和 3nm 的圆柱孔中的吸附，其中一个样品孔与体相流体接触。根据孔径和固-流强度的选择，得到了 I、V 和 H1 型吸附等温线。此外，还研究了体相平衡、吸附相的向列序参数和沿孔轴方向的自扩散系数。结果表明，分子形状和表面吸引力都对吸附等温线的形状起着决定性的作用。一般来说，环分子的吸附量较大，而完全柔性的模型吸附量最小。形态和表面强度对分子的扩散影响较小。在超约束下，线性硬分子表现出异常高的吸附和扩散，表明渗透性增强，这归因于吸附流体向向列液晶的相转变。
