Title

Synthesis and Characterization of Polymer-Clay Systems Prepared by Surface-Initiated Polymerization

Date of Completion

January 2011

Keywords

Chemistry, Polymer|Nanotechnology|Engineering, Materials Science

Degree

Ph.D.

Abstract

Polymer-clay nanocomposites were prepared by surface-initiated ring opening metathesis polymerization (SI-ROMP) of norbornene monomers on a previously surface-modified naturally occurring montmorillonite (MMT) clay template. Utilizing the hydrothermal–silylation reaction between a norbornenyl-bearing chlorosilane agent and silanol groups of the MMT clay template, we were able to successfully surface-bound a metal alkylidene catalyst used to mediate the ROMP and grow poly(norbornene) chains directly from the surface. Our approach produced a nanocomposite having poly(norbomene) chains that are covalently-attached to the inorganic substrate, as opposed to the conventional polymer-clay composites having ionically tethered chains (via the ammonium-based modifiers of the organoclay) or physically adsorbed polymers.^ Structural characterization of the surface-modified clay templates, nanocomposites and cleaved polymers was done using various characterization techniques that include x-ray diffraction, infrared and NMR spectroscopy, thermogravimetric analysis (TGA), gel permeation chromatography (GPC) and transmission electron microscopy (TEM). Analyses of the nanocomposite structure that include surface chemistry of the clay template, morphology of the nanocomposite, polymer chemistry, the molecular weight and polydispersity of the cleaved polymer and grafting density were considered. Also, preliminary studies of the mechanical and thermal properties of the nanocomposites were performed using dynamic mechanical analysis (DMA), and TGA. ^