Title

Synthetic designs for functional polymer/inorganic nanocomposites

Date of Completion

January 1999

Keywords

Chemistry, Polymer

Degree

Ph.D.

Abstract

This dissertation addresses the synthesis and processing aspects of fimctionalized polymer/inorganic nanocomposites, specifically polyphenol nanocomposite materials incorporating (a) nanostuctured cadmium sulfide (CdS), and (b) nanocrystalline vanadium pentoxide (V2O5). It also explores their structure-property relationships including optical properties. This study therefore included: the hematin catalyzed polymerization of ethylphenol; synthesis of US nanoparticles within reversed micelles and their dispersion in a polymer matrix; investigation of the surface chemistry of US, which is related to the properties of polymer-CdS nanocomposites; synthesis of nanostructured polymer/V2O5 via a combinatorial chemo-enzymatic sol-gel process; and optical characterization of the materials obtained. ^ The dehydrogenation of phenol compounds (p-ethylphenol), and polymer formation from these monomers, was studied using a novel biocatalyst hematin. The mechanism studies and kinetics of the polymerization reaction indicated that phenol radicals were formed by a two step electron transfer reaction catalyzed by hematin in the presence of a peroxide. ^ CdS semiconductor nanocrystallites were synthesized in reversed micelles with subsequent in situ enzymatic copolymerization of p-ethylphenol and 4-hydroxythiophenol in the same medium. Consequently, CdS nanocrystallites were incorporated into the polymer matrix to form spherical polymer/inorganic composites with surface hydroxyl groups. The polymer/CdS core was then dispersed into polycarbonate by copolymerization. The polymer/CdS nanocomposites showed higher optical absorbance in the UV-VIS range when compared to the polymer matrix without CdS. ^ Vanadium pentoxide (V2O5) xerogels were prepared by the sol-gel process. The generation of V2O5 was optimized by a combinatorial approach incorporating rapid screening by Raman spectroscopy. Subsequently, poly(p-ethylphenol) (PEP)/V2O 5 nanocomposites were prepared by the chemo-enzymatic/sol-gel process. ^ Composites with dispersed CdS (1.0 wt%) had a third order nonlinear optical susceptibility, χ(3), of ∼ 2.5 × 10−10 e.s.u. Vanadium pentoxide nanocomposites (1.0 wt%) exhibited a χ(3) of ∼ 2.0 × 10−10 e.s.u. ^