Density Functional Approach to Adsorption and Retention of Spherical Molecules on Surfaces Modified with End-Grafted Polymers

Abstract

A density functional approach to describe adsorption of Lennard-Jones fluids on a surface modified with grafted chains is proposed. The theory is extended to the solute retention in chromatography with chemically bonded phases. The chain molecules are modeled as freely jointed tangent spheres with end segments linked to the surface. The segments interact via Lennard-Jones potential. The effects of grafting density and molecular interactions are discussed. The results are compared with the Monte Carlo simulation data. The theory predicts the most important features of the retention process.

Changes in the structure of tethered chain molecules as predicted by density functional approach

“…Following our previous works [20,21,39,42] we consider a fluid of spherical molecules of diameter σ f in contact with a modified substrate. The surface is covered by the film of preadsorbed chain molecules.…”

“…The studies included scaling theories [13][14][15], classical self-consistent field methods [16,17], single chain mean-field methods [18], density functional theories [18][19][20][21][22] and computer simulations [23][24][25][26][27][28][29][30][31][32][33][34]. In our opinion, particularly important for further theoretical studies of systems involving tethered chains is the development of density functional theory (DFT) [20,21,[35][36][37][38][39][40][41][42] that is based on the approach proposed by Yu and Wu [43].…”

“…Recent theoretical works based on the DFT [20,21,[35][36][37][38][39][40][41][42] have mainly concentrated on the description of adsorption of fluids on modified surfaces, while the problem of the changes in the layer of pinned chains itself has attracted less attention. Of course, the accumulation of fluid molecules near the adsorbing surface induces changes in the tethered layer, especially when the adsorbed fluid undergoes prewetting of layering transitions [40,42].…”

“…Such studies, however, can be carried out by using theoretical approaches based on microscopic models. Therefore, the aim of the present work is to employ the DFT used in our previously works [20,21,[39][40][41][42] to investigate how the thickness of the pinned layer changes with their length and with their surface density. Our principal purpose is to check whether the theory employed by us is capable of reproducing the results of coarse-grained approaches [13][14][15].…”

Exploring fluid-solid interfaces with Stefan Sokołowski

“…To do that, extensive computer simulations and density functional approaches have been employed. Different patterns of the structural organization of modifiers at various external conditions were put in correspondence to the trends of the behavior of measurable properties [43][44][45][46][47]. In this manner, the group intends to optimize the computer design of nanoporous systems with desired properties and to search for novel materials with applications in chromatography.…”