Pizio Orest, Pusztai László, Sokołowska Zofia, Sokołowski Stefan
Instituto de Química de la UNAM, Coyoacán 04510, Mexico.
J Chem Phys. 2009 Apr 7;130(13):134501. doi: 10.1063/1.3103266.
The behavior of Lennard-Jones fluid in slitlike pores with walls modified by tethered chain molecules is studied using density functional theory. The effects of confinement and chemical modification of pore walls on the solvation force are investigated. Two models of the pore walls are considered. According to the first model, the chain molecules are chemically bonded by their end segments to opposite walls of the pore, forming flexible pillars. In the second model the chains build up a brush at each wall due to bonding of the first segment at one wall. The nonbonded terminating segment of a molecule is strongly attracted via a short-range potential to any wall of the pore. Then a pillarlike or looplike structure of chains can be formed. In the first model the solvation force at the wall-to-wall is repulsive for narrow pores and strongly attractive for wider pores of the order of the nominal chain length. Oscillations of the solvation force are induced by adsorbed fluid structure and by ordered structure of segments on the fragment of entirely attractive force curve. In the second model, however, the solvation force decays to zero as the pore width increases. Attractive force can be induced at intermediate separation between walls due to modification of the pore walls.
利用密度泛函理论研究了在具有由拴系链分子修饰壁面的狭缝状孔中 Lennard-Jones 流体的行为。研究了孔的限制作用和壁面化学修饰对溶剂化力的影响。考虑了两种孔壁模型。根据第一种模型，链分子通过其末端段化学键合到孔的相对壁上，形成柔性支柱。在第二种模型中，由于链的第一段在一个壁上的键合，链在每个壁上形成刷子状。分子的非键合末端段通过短程势被强烈吸引到孔的任何壁上。然后可以形成链的柱状或环状结构。在第一种模型中，对于窄孔，壁间的溶剂化力是排斥的，而对于标称链长量级的较宽孔则是强烈吸引的。溶剂化力的振荡是由吸附流体结构和完全吸引力曲线片段上链段的有序结构引起的。然而，在第二种模型中，随着孔宽度增加，溶剂化力衰减至零。由于孔壁的修饰，在壁间的中间间距处可以诱导出吸引力。
