Monte Carlo simulations of polymer brushes

Three-dimensional Monte Carlo simulations of flexible and semiflexible polymer brushes at various grafting densities are carried out to study their equilibrium structure and attendant properties by using the bond fluctuation model. Our simulation results of long flexible polymer brushes are, in general, consistent with predictions of the self-consistent field theory. However, a depletion layer near the substrate is only observed at small grafting densities but not at medium densities. We have also measured the brush height and end-to-end distance of various polymer brushes, and their dependence on grafting density, chain length, and chain stiffness are obtained. The distribution of bending angles at various temperatures are calculated for four different forms of bending energy and our simulation results agree with theoretical predictions very well. Moreover, we study the isotropic-to-nematic transition of polymer brushes, which is found to be a continuous phase transition from our simulation results. Finally, we discuss the effects of local grafting density fluctuation on the monomer and end density distributions.