MONTE-CARLO SIMULATION OF CONFINED SEMIFLEXIBLE POLYMER MELTS

The behavior of semiflexible polymer melts confined between surfaces is investigated via Monte Carlo simulation. A depletion of chain sites near the wall at low densities and an enhancement of chain sites near the wall at high densities is observed, which can be explained in terms of a competition between packing and configurational entropic effects. An increase in the molecular stiffness results in improved packing of segments against the walls, but increases the loss in configurational entropy suffered by a single molecule near the wall. Changing the molecular stiffness changes the average bond angle and hence alters the way the molecules pack against the surface. The density profiles are a result of these competing effects. One consequence is that for some values of the stiffness, the solvation force (estimated from the density profiles via a superposition approximation) ceases to be an oscillatory function of wall separation even at liquidlike densities. The conformational properties of the molecules are also investigated. If each molecule is modeled in terms of an equivalent spheroid with the same moment of inertia, it is found that conformational changes occur only when the molecular centres of mass are at distances from the surface that are smaller than the thickness of the spheroid.