MOLECULAR-DYNAMICS SIMULATION FOR BILAYERS OF ALKYL THIOL MOLECULES AT SOLID-SOLID INTERFACES

We present the results of molecular dynamics simulations for three dif ferent systems of bilayers of long-chain alkyl thiol [S(CH2)(15)CH3] m olecules on an solid-solid interface using the extended collapsed atom model for the chain-molecule. It is found that there exist two possib le transitions: a continuous transition characterized by a change in m olecular interaction between sites of different chain molecules with i ncreasing area per molecule and a sudden transition from an ordered la ttice-like state to a Liquid-like state due to the lack of interaction s between sites of chain molecules on different surfaces with increasi ng distance between two solid surfaces. The third system displays a sm ooth change in probability distribution characterized by the increment of gauche structure in the near-tail part of the chain with increasin g area per molecule. The analyses of energetic results and chain confo rmation results demonstrate the characteristic change of chain structu re of each system.