Molecular dynamics is used to model the friction between two ordered monolayers of alkane chains six units long bound at their ends to two rigid substrates. Depending on the interfacial interaction strength, energy dissipation occurs by a discontinuous ‘‘plucking’’ mechanism and a continuous viscous mechanism. The plucking mechanism follows a simple thermal activation model, while for the viscous mechanism, friction force is enhanced at the rotator transition temperature of the films.

• Received 13 January 1993

DOI:https://doi.org/10.1103/PhysRevLett.70.1960