Interfacial sliding of polymer brushes: A molecular dynamics simulation

Polymers end grafted to a surface have recently been shown to have an anomalously low effective friction coefficient mu(b). TO understand the origin of the observed reduction in friction, molecular dynamics simulations of polymers tethered at one end to a surface in a good solvent were carried out. As the surfaces are brought into contact, the normal force increases rapidly, while the shear force is found to be significantly smaller. For low shear velocity upsilon, the surfaces slide past each other with no change in the chain's radius of gyration or the amount of interpenetration. In this regime the shear force increases linearly with upsilon. For larger upsilon, there is significant chain stretching and disentanglement.