Condensed Matter Physics, 2010, vol. 13, No. 1, p. 13602:1-12
Entropic solvation force between surfaces modified by grafted chains: a density functional approach
(Instituto de Química de la UNAM, Coyoacán 04510,
(Department for the Modeling of Physico-Chemical Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland)
The behavior of a hard sphere fluid in slit-like pores with walls
modified by grafted chain molecules composed of hard sphere segments
is studied using density functional theory. The chains are grafted
to opposite walls via terminating segments forming pillars. The
effects of confinement and of "chemical" modification of pore
walls on the entropic solvation force are investigated in detail. We
observe that in the absence of adsorbed fluid the solvation force is
strongly repulsive for narrow pores and attractive for wide pores.
In the presence of adsorbed fluid both parts of the curve of the
solvation force may develop oscillatory behavior dependent on the
density of pillars, the number of segments and adsorption
conditions. Also, the size ratio between adsorbed fluid species and
chain segments is of importance for the development of oscillations.
The choice of these parameters is crucial for efficient manipulation
of the solvation force as desired for pores of different width.
density functional approach, grafted chains, solvation force, density profiles
PACS: 68.08.-p, 68.15.+e, 82.35.Gh, 68.43.-h