Diffusion on a self-assembled monolayer: molecular modeling of a bound + mobile lubricant.
The diffusion of tricresyl phosphate molecules on an octadecyltrichlorosilane self-assembled monolayer (SAM) was characterized using molecular dynamics simulations. The simulations predict that when placed on the top of a close-packed SAM, the molecules remain mobile on the surface with an isotropic diffusion activation energy of approximately 9 kJ/mol. In contrast, an anisotropic barrier that results from chain tilt within the SAM is predicted for diffusion into a defect created by reducing the alkane chain length within a cylinderical region of the surface. Once in the defect, the molecules become trapped by embedding part of the molecule into the side of the SAM.
Irving
Douglas L
DL
Department of Materials Science and Engineering, Campus Box 7907, North Carolina State University, Raleigh, North Carolina 27695-7907, USA. dlirving@ncsu.edu
Brenner
Donald W
DW