Date of Award

2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry

First Advisor

Jaycoda S. Major

Abstract

The focus of the research reported in this dissertation has focused on two areas: (1) Synthesis of silane-containing polymers and (2) the application of these polymers to surface modification of substrates such as PDMS (for microfluidic applications), glass, quartz, silicon wafers and various nanoparticles (magnetic iron oxide, silica) for use in chemical and biological sensing and separation applications as well as in biofunctionalization of magnetic nanoparticles.

Chapter 1 of this dissertation described the preparation of a library of silane containing co- and terpolymer prepared with various substituted maleimides along with their characterization by FTIR, UV-Visible, 1H- and 13C-NMR, TGA and DSC. The ability to control the reactive functionalities incorporated into the polymer structure affords direct control over the resulting properties of the materials. Chapter 2 describes the conversation of the polymers prepared in chapter 1 into various functional forms that can be used in the design of different sensing platforms. More specifically, this chapter lays out the conversion of these polymers into polymer thin-films, polymer-silica composites, polymer-coated nanoparticles and polymer facilitated nanoparticle arrays. In all cases the conversion or assembly of these polymers into these structures is made possible through the reaction of the alkoxysilane side groups of the polymers forming very robust siloxane bonds. These structures are being explored for their use in chemical sensing and separations of explosive and amines and other species as described in other chapters of this dissertation. The conversion f the polymer into thin-films is accomplished through either dip-coating using a layer-by-layer deposition scheme or through a spin-coating scheme. The layer-by-layer scheme allowed for a controlled deposition of the polymers into films of desired dimension where a constant loading density is observed as a function of the deposition cycle (i.e. number of layers). A facile biofunctionalization of magnetic and silica nanoparticles is also describe in this dissertation. The ability to biofunctionalize these materials allows for their potential application in the biomedical field where they can be used in detection and in target drug delivery.

Also described herein is the functionalization of microfluidics systems for bioanalysis. Surface modification with silica nanoparticles would be a promising technique to provide an excellent interface on the conventional polymer surface. A sensitive biofunctionalization is carried in microfluidic chips. The antigens attached to the surface modified silanes via urea linkage and successful binding of antigens and antibodies is observed and can preserve the bioactivity of the antigens and antibodies and resist non specific adsorption. This study can be extended for a high-throughput system for bio-marker proteins.

Finally, we demonstrate the applicability of these polymers for sensing amines and nitro compounds. Substitutions on the phenyl ring help in tuning the sensitivity of these polymers to various amines including very weak aromatic amines. Increase in the intensity of the fluorescence and a very noticeable change in color of the polymer solutions in presence of amines helps in their detection. The color of the solution depended on two factors: identity of the polymer and identity of the base. For different polymers, the color varied with the electron withdrawing/donating power of the substitutions on the phenyl ring and also the variation in the side chain allyl vs. vinyl and ethoxy vs. methoxy. Also the nature of the amines 10 vs. 20 vs. 30 affected the rate at which the polymers reacted with those amines and formed the final yellow product. The colored polymer solutions with high fluorescence intensity have been used to detect the presence of nitro compounds as their presence brought the fluorescence down and was directly proportional to the amount of nitro compound present. This work represents our ability to design, control and utilize novel materials for various applications.

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