Functionalization and patterning of monolayers on silicon(111) and polydicyclopentadiene

Abstract

The formation of a functional surface combines the properties of a substrate and monolayer to produce a new hybrid that can combine aspects of each. Monolayers can be made on many surfaces, and well defined functionalized monolayers were assembled on silicon(111) and polydicyclopentadiene (PDCPD). Acid terminated monolayers were assembled on silicon(111) and their functionalization chemistry explored. It was shown that using trifluoroacetic anhydride to generate an intermediate reactive anhydride, the surface could be functionalized with amines. It was further shown that using soft lithography these functionalized surfaces could be patterned. Mixed monolayers of methyl and olefin terminated surfaces on silicon(111) were used to develop a new soft lithographic technique with polydimethylsiloxane (PDMS). PDMS can be controllably etched using fluoride species. The surface is first activated by the attachment of the Grubbs' 1 st generation catalyst. A PDMS microfluidic device is then placed on the surface. By using a cross metathesis reaction, the exposed channel can be pacified. The next step, a fluoride etchant is used to remove PDMS, exposing an unreacted surface. Polymer brushes were then grown by ring opening metathesis polymerization (ROMP) in this region. Functionalization of the emerging polymer PDCPD was conducted through two different routes. ROMP formed PDCPD has double bonds that can be functionalized. In the first process, the double bonds were reacted with bromine. This is a rapid reaction and proceeds to a significant depth in the material. Bromines can then be displaced with amines in a substitution reaction. This was demonstrated with a fluorinated amine that when examined by XPS were shown to be present only at the surface, further more we were able to pattern this surface too. Secondly, a process using epoxides was developed. The epoxidation reaction could not be quantified, but formation in the second step of an Results and Discussion .