Author : Richard Oluwarotimi Ademola Osibanjo
Publisher :
Page : pages
File Size : 45,25 MB
Release : 2013
Category :
ISBN : 9781303792458
The big picture for this work is the development of a biosensor that will determine contaminants in aqueous systems via surface-bound thin films. In order to make this a reality, it is important to have an understanding of the initial stages during polymerization. Details of the mechanisms and structures created in the earliest stages of surface-bound polymer films affect the nature and structure of the films in profound ways. The two major methods on tethering polymers onto various substrates are the "grating from" and the "grafting to" methods. This study used the grafting from approach owing to its ability to produce denser grafting densities and thus produce thicker films. This study investigates the stability, structure, kinetics and density of initiator binding to Au surfaces and formulation of polymers via atom transfer radical polymerization (ATRP) on Au surfaces at low temperatures (25 -50 °C). Though restricted by the lability of thiol-gold at 50 °C, advantages of lower temperatures includes; absence of side reactions, chain transfer reactions, thermal crosslinking and increased quality of the produced polymer film. Time-dependent molecular information is obtained in situ from deposition of thiol-based initiator on the substrate, addition of monomer and catalyst during surface initiated ATRP on a Au substrate.Surface initiated atom transfer radical polymerization (SI-ATRP) is accompanied by tethering an initiator molecule such as 11-Mercaptobromoisobutyrate bromides onto a gold surface via formation of a Au-S bond. As a monolayer of the compound binds to the surface, the chains line up to form a quasi-crystalline self-assembled monolayer. The bromine can be abstracted with a catalyst, such as CuBr/CuBr2 or photochemically to produce a radical which then takes part in polymerization. ATR-FTIR is the method of choice because it is a surface specific technique and information regarding the nature of the adsorbed initiator molecule and details concerning polymer orientation desorption, mechanisms and kinetics can be obtained. These studies will contribute to further understanding the implementation of overlayer enhancement for IR spectroscopy at interfaces and understanding of the structure and dynamics of supported polymer films. It will also help provide an in depth look into the reactions of thin films and the development of thin film sensor technologies. Research into newer catalysts may be required for Cu-SI-ATRP owing to findings showing that Cu catalysts aide the desorption of thiol based initiator molecules which result in extensive termination reactions and production of thin films.