Force between grafted polymer brushes

The force between a pair of planar, athermal grafted polymer brushes is determined in Monte Carlo simulations of the fluctuating bond lattice model. Monodisperse systems with chain lengths of 20 and 40 segments are studied at surface coverages ranging from 0.05 to 0.2. The variation of the force with chain length, surface coverage, and separation is in agreement with predictions of self-consistent field theory, except at large separations, when only the tails of the brushes are in contact. As the brush separation is reduced, the force per unit area approaches the pressure of the bulk polymer fluid. Density profiles of free and compressed brushes are analyzed.