The effect of attractions on the structure of fused sphere chains confinedbetween surfaces

The effect of attractive interactions on the behavior of polymers between s urfaces is studied using Monte Carlo simulations. The molecules are modeled as fused sphere freely rotating chains with fixed bond lengths and bond an gles; wall-fluid and fluid-fluid site-site interaction potentials are of th e hard sphere plus Yukawa form. For athermal chains the density at the surf ace (relative to the bulk) is depleted at low densities and enhanced at hig h densities. The introduction of a fluid-fluid attraction causes a reductio n of site density at the surface, and an introduction of a wall-fluid attra ction causes an enhancement of site density at the surface, compared to whe n these interactions are absent. When the wall-fluid and fluid-fluid attrac tions are of comparable strength, however, the depletion mechanism due to t he fluid-fluid attraction dominates. The center of mass profiles show the s ame trends as the site density profiles. Near the surface, the parallel and the perpendicular components of chain dimensions are different, which is e xplained in terms of a reorientation of chains. (C) 1999 American Institute of Physics. [S0021-9606(99)70128-5].