(281e) Visualization of Cooperativity in the Building of Mixed Self-Assembled Monolayers

Authors: 
Campbell, C. J., Northwestern University
Grzybowski, B. A., Northwestern University


In this talk, we will describe a mechanism involving cooperativity for the building of mixed self-assembled monolayers containing thiols and disulfides by wet stamping (WETS). To gain an insight to the composition of mixed monolayers, one either relies on bulk monolayer characteristics (i.e. contact angle or ellipsometry) or probing the surface on a molecular scale (i.e. STM or LFM). By utilizing a fluorescently-tagged disulfide, we are able to visualize the composition of a mixed monolayer on the microscale simply through the use of a fluorescent microscope. When alkyl-terminated thiols are mixed with fluorescently-tagged disulfides, a mixed monolayer forms under the micropattern. However, when -COOH or -OH terminated thiols are mixed with fluorescently-tagged disulfides, there are two distinct regimes. In one regime, a mixed monolayer forms under the micropattern. In the other case, only a thiol monolayer under the micropattern. This is due to cooperative adsorption via the -COOH or -OH terminated thiol already on the surface, which enhances the kinetics of building the thiol monolayer and effectively excludes the fluorescently-tagged disulfide from the monolayer.