A density functional study of the structure of tethered chains in a binary mixture

A density functional study of the structure of a layer formed by chain molecules pinned to a solid surface is presented. The chains are modeled as freely joined spheres. Segments and all components interact via Lennard-Jones (12-6) potential. The interactions of fluid molecules with the wall are described by the Lennard-Jones (9-3) potential. We analyze how different parameters of the model affect the dependence of the brush height upon the mixture composition. We consider the effect of grafting density and the parameters characterizing the interactions of fluid molecules with the substrate and with the chains as well as interactions within the mixture. The changes in the brush height correlate with the adsorption of particular components.Comment: 12 pages, 8 figure

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

We use a version of the density functional theory to study the changes in the height of the tethered layer of chains built of jointed spherical segments with the change of the length and surface density of chains. For the model in which the interactions between segments and solvent molecules are the same as between solvent molecules we have discovered two effects that have not been observed in previous studies. Under certain conditions and for low surface concentrations of the chains, the height of the pinned layer may attain a minimum. Moreover, for some systems we observe that when the temperature increases, the height of the layer of chains may decrease.Comment: 13 pages, 7 figure

First-order phase transitions in lattice bilayers of Janus-like particles: Monte Carlo simulations

The first-order phase transitions in the lattice model of Janus-like particles confined in slit-like pores are studied. We assume a cubic lattice with molecules that can freely change their orientation on a lattice site. Moreover, the molecules can interact with the pore walls with orientation-dependent forces. The performed calculations are limited to the cases of bilayers. Our emphasis is on the competition between the fluid-wall and fluid-fluid interactions. The oriented structures formed in the systems in which the fluid-wall interactions acting contrary to the fluid-fluid interactions differ from those appearing in the systems with neutral walls or with walls attracting the repulsive parts of fluid molecules.Comment: 12 pages, 11 figure

Adsorption from binary solutions on chemically bonded phases

We use density functional theory to investigate adsorption of liquid mixtures on solid surfaces modified with end-grafted chains. The chains are modelled as freely joined spheres. The fluid molecules are spherical. All spherical species interact via the Lennard-Jones (12-6) potential. The Lennard-Jones (9-3) potential describes interactions of solvent molecules with the substrate. We study the relative excess adsorption isotherms, the structure of surface layer and its composition. The impact of the following parameters on adsorption is discussed: the grafting density, the grafted chain length, interactions of solvent molecules with grafted chains and with the substrate, and the presence of active groups in grafted chains. The theoretical results are consistent with experimental observations

Exploring fluid-solid interfaces with Stefan Sokołowski

This special issue of "Condensed Matter Physics" is a collection of works prepared to mark the 65th birthday of Prof. Stefan Sokołowski, our good friend, co-worker and member of the Editorial Board of this journal. By presenting this issue we would like to add our contribution towards the celebration of his scientific achievements and valuable contributions to the science. The majority of the works in the issue deal with the description of fluid-solid interfaces by using modern statistical mechanics methods - the principal line of Stefan's research. However, some contributions from the related areas authored by his close friends are included as well