ORDER IN MICROCONTACT PRINTED SELF-ASSEMBLED MONOLAYERS

Self-assembled monolayers (SAMs) on Au(111) formed by microcontact pri nting of dodecanethiol and investigated by scanning tunneling microsco py and wettability measurements have, under certain conditions, charac teristics indistinguishable from SAMs formed from solutions of dodecan ethiol in ethanol. The monolayer product of microcontact printing demo nstrates a sensitivity to the concentration of thiol used to ink a pol y(dimethylsiloxane) (PDMS) stamp needed to make the print and an insen sitivity to its duration of contact, for times > 0.3 s, with the gold substrate. The wettability of the SAM, the distribution of domains wit hin the monolayer, their size and organizational state, and the patter n of depressions on the surface each are reproducibly controlled by si mply changing the concentration of dodecanethiol applied to the stamp. The inferred mode of growth of printed SAMs shares many features of m onolayer formation through the gas phase of a thiol and corresponds to a highly controlled and self-limiting delivery of thiol from the inte rior parts of the PDMS. Our study shows that printed SAMs provide a wo nderful opportunity to change controllably the order in monolayers at the nanometer scale and to examine its effects on microscopic and macr oscopic properties of these films.