Surface functionalization and imaging using monolayers and surface-grafted polymer layers

A method of surface functionalization of ceramics with monolayers and surface grafted polymer layers is described. A phenylsilane monolayer is created on the substrate's oxide surface by using phenyltrichlorosilane as the silane coupling agent. To control the formation of the monolayer and ensure the growth of a dense, homogeneous layer, the ceramic surface is first dried and then a controlled amount of water is adsorbed onto it, and a hindered organic base is added to the phenyltrichlorosilane solution to absorb acid generated in the reaction of the silane coupling agent with hydroxyl groups on the ceramic surface. This procedure results in dense homogeneous phenylsilane monolayers on a variety of surfaces, including silicon, Pt/PtO, and quartz. These layers can now be functionalized by addition of triflic acid, which removes the phenyl ring as benzene, and introduction of a nucleophile. Monolayers of -C=CH, -OCH2CF3, [(OCH2CH2)(2)O], -OCH2CF2CF3, and -O(CH2)(6)NH2 were generated in this fashion, all proving to be continuous and homogeneous. In addition, the cationic silyl triflate site generated by the removal of the phenyl ring is capable of initiating polymerization to form covalently bound polymer layers on the surface. Polymer layers of poly(methyl methacrylate), poly(propylene oxide), and poly(dimethylsiloxane) were generated in this manner; in the case of poly (dimethylsiloxane), layers up to 300 Angstrom thick were formed. Anionic initiation of polymerization is also possible, using a bromopropyl trichlorosilane coupling agent to form the initial monolayer, followed by lithiation with lithium di-tert-butylbiphenyl. Acrylonitrile can be anionically polymerized to films of up to 2450 Angstrom in thickness. The monolayers and polymer layers were characterized by XPS, AFM, contact angle measurements, and profilometry and were found to be continuous. The initial phenylsilane monolayer can be lithographically patterned by using 193 nm Light to cleave the surface phenyl groups; the remaining groups can then be functionalized as discussed above to create surface-grafted patterned polymer layers.