MD simulations of diffusion of cyanobiphenyl molecules adsorbed on the graphene surface coated with alkane and alcohol molecules

Abstract

Molecular dynamics simulations were carried out to study the structural and diffusion properties of a cyanobiphenyl monolayer composed of pentyl cyano biphenyl (5CB) and pentyloxy cyano biphenyl (5OCB) molecules on a graphene surface coated with alkane and alcohol molecules. To investigate the diffusion properties of 5CB and 5OCB molecules on the graphene surface, the molecules of pentane ( $C_5$) and dodecane ( $C_{12}$) from alkanes and dodecanol ( $C_{12}\mathrm{OH}$) from alcohols with a polar hydroxyl ( $-\mathrm{OH}$) terminal functional group were chosen as orienting surfactant molecules. It was found that the diffusion ability of cyanobiphenyl molecules in a graphene substrate coated with alkane and alcohol molecules depends on the chain length of these molecules and on the presence of polar hydroxyl –OH terminal groups. With an increase in the length of alkane molecules from $C_5$ to $C_{12}$, the value of the diffusion coefficient $D_z\left(5\mathrm{CB}\right)$ (or $D_z\left(5\mathrm{OCB}\right)$), it decreases slightly, while the presence of the polar hydroxyl $-\mathrm{OH}$ terminal group leads to a significant decrease in this diffusion coefficient of cyanobiphenyl molecules.