Substrate surfaces: A study encompassing modification and utilization

• Main Author: Ingall, Michael D. K
• Language: ENG
• Published: ScholarWorks@UMass Amherst 2001
• Subjects: Chemistry|Polymers
• Online Access: https://scholarworks.umass.edu/dissertations/AAI3027211

This thesis reports upon the modification of substrates by the modification of their surfaces. The initial impetus for this work originates in the study of the backbone network polymers, polysilynes. Published work shows the ability to remove the pendant groups present, with the use of trifluoromethanesulfonic acid, on the backbone and replace them with specific nucleophiles. As an extension of this, work was undertaken on solid silicon wafers to if the same chemistry could be applied. Initially, the silicon used has a dioxide layer present. This has to be treated with the strongly oxidizing piranha solution (concentrated sulfuric acid and 30% hydrogen peroxide) that generates a high density of hydroxyl groups on the surface. It is these surface hydroxyls that react with the silanizing agents (in this study they are exclusively trichlorosilanes) to generate organosilane layers on the silicon substrate. In a direct analogue of the polysilyne work, phenylsilane layers that have been generated are exposed to trifluoromethanesulfonic acid giving rise to triflated substrates. These can react with nucleophiles to generate monolayers of these nucleophiles. Instead of laying down monolayers, the triflated substrates can be utilized as cationic polymerization catalysts and so form films of polymers. However, the number of monomers that are susceptible to cationic polymerization is limited as well as the technique being prone to self-termination. Anionic polymerization would be better and the synthesis of anionic initiators is described as well as their use to polymerize methyl methacrylate, acrylonitrile and hexamethylcyclotrisiloxane. In a further effort to extend the number of available monomers, and hence polymers, the use of organometallic initiators is investigated. This entails the generation of the requisite organosilane layer, deposition of the specific organometallic system and then exposure to ethylene or methyl methacrylate. Two different organometallic systems will be discussed. The ability to take this work and apply it to industrially relevant substrates, i.e. metals, is also addressed. The generation of thick poly (methyl methacrylate) films on a variety of different metals is demonstrated. The generation of poly (ethylene) films upon a copper substrate is also demonstrated.