A polymer chain trapped between two parallel repulsive walls: A Monte-Carlo test of scaling behavior

An off-lattice bead-spring model of a polymer chain trapped between two parallel walls a distance D apart is studied by Monte-Carlo methods, using chain lengths N in the range 32 less than or equal to N less than or equal to 512 and distances D from 4 to 32 (in units of the maximum spring extension). The scaling behavior of the coil linear dimensions parallel to the plates and of the force on the walls is studied and discussed with the help of current theoretical predictions. Also the density profiles of the monomers across the slit are obtained and it is shown that the predicted variation with the distance z from a wall, rho(z) proportional to z(1/nu), is obtained only when one introduces an extrapolation length lambda in the description, rho(z) proportional to [(z + lambda)/D](1/nu), with lambda approximate to 0.35. An analogous result is also obtained for Gaussian chains (where 1/nu = 2).