Results are presented of Monte Carlo calculations for self-assembled monolayer systems consisting of binary mixtures of long-chain alkyl thiols of different lengths adsorbed on a gold surface. A sampling scheme is used in which large- scale conformational changes are made to a trial molecule in a single move, supplemented by attempted interconversions of long and short chains. A marked trend towards segregation of the two species is observed, and the outer regions of the monolayers are found to be conformationally more disordered than the inner parts; both effects are most pronounced when the concentration of long chains is low.
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We thank C. D. Bain and M. L. Klein for many stimulating discussions. The work has been supported by SERC under Special Grant No. GR/E68716. One of us (JIS) acknowledges support by a Stipendium der Friedrich-Naumann-Stiftung and by a Foreign arid Commonwealth Office Scholarship.