Chiral Adsorption Conformations of Long-Chain <i>n</i>-Alkanes Induced by Lattice Mismatch

Abstract

The adsorption and self-assembly of n-alkanes on graphite not only find value in applications related to lubrication and surface passivation but are also of fundamental importance in the study of molecule/substrate interactions. Their adsorption is classically described by Groszek’s model of commensurate registry, which is confirmed by high-resolution scanning tunneling microscopy studies. Nonetheless, the role of the chain length-dependent lattice mismatch between n-alkanes and graphite has not been considered. Here, a systematic study of various length n-alkanes at the liquid/graphite interface reveals the existence of a stability limit for the classical straight chain conformation postulated by Groszek’s model. Once the critical length is reached, the increasing lattice mismatch induces a swerved chain conformation that is chiral. Experimentally, as well as computationally, the crossover from a straight to a swerved chain conformation is determined to be between 40 and 50 carbon atoms.