Effects of surface affinity on the ordering dynamics of self-assembled monolayers of chain molecules: Transition from...

The effects of surface interactions on the ordering dynamics of self-assembled monolayers (SAM) of chain molecules were studied using molecular dynamics simulations. When the strength of surface-chain interactions was equal to or less than that of chain-chain interactions, domains of chain molecules adsorbed perpendicular to the surface ("upright" chains) formed on the surface. Although chain molecules adsorbed parallel to the surface ("lying" chains) were initially observed on the surface, they did not develop into two-dimensionally aligned structures. In contrast, when the strength of surface-chain interactions was at least twice that of chain-chain interactions, the proportion of upright chain molecules was initially small, and the reorientation of lying chains was observed shortly afterwards. In this case, the reorientation from lying to upright configuration developed slowly from the domain boundaries of two-dimensionally aligned structures late in the calculation period. Although the orientation processes of chain molecules on surfaces were strongly influenced by the strength of surface-chain interactions, the total adsorption rate on the surface was not. We also analyzed the maximum area of domains formed by lying chains. The development of two-dimensionally aligned domains required strong surface-chain interactions to prevent the spontaneous formation of nuclei of upright domains.