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Synthesis of multimetallic nanocomposite materials utilizing block copolymers.

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Call No.	QD382.B5 S47 2006
Author	Sessions, Laura B.
Title	Synthesis of multimetallic nanocomposite materials utilizing block copolymers.
Date	2006
Abstract	Nanocomposite materials containing both gold and cobalt were synthesized using block copolymers as agents for controlling spatial organization of the nanoparticles. The targeted polymers are polystyrene- block -poly(alkyne-functional)styrene copolymers where the alkyne groups were specific for incorporation of cobalt carbonyl, a precursor for cobalt nanoparticles. Cobalt-composite materials utilized diblock copolymers made by nitroxide-mediated polymerization (NMP), but extensive investigation revealed participation of the alkyne-functional groups in this polymerization method. By using polymerization solvent and low conversions, NMP could be used to make the desired diblock copolymers. A post-polymerization modification route utilizing NMP polymers of 4-bromostyrene with Sonogashira coupling of terminal alkynes to yield the desired polymers was therefore investigated. Successful coupling was obtained with room temperature conditions for terminal alkynes, 1-hexyne and phenylacetylene, on homopolymers with low molecular weight. Phenylacetylene was also successfully coupled on homopolymers of high molecular weight (up to 70 kg/mol) and multiblock copolymers. Finally, this class of diblock copolymers was extended by inclusion of a thiol endgroup, from synthesis by reversible addition-fragmentation chain transfer polymerization (RAFT), allowing attachment to gold nanoparticles (AuNPs) and thereby creating the possibility for inclusion of multiple metals in these systems. Gold nanoparticles were synthesized in situ from hydrogen tetrachloroaurate using thiol endgroups on the RAFT diblock copolymers and superhydride as reducing agent. Ex situ syntheses using blends of diblock copolymers with pre-made gold nanoparticles were also investigated. After incorporation of cobalt carbonyl into the gold-composite materials by formation of cobalt carbonyl adducts with pendant alkyne groups in one block of the polymer, carbon monoxide ligands were removed by solvothermolysis or thermolysis in thin films to yield cobalt nanoparticles or elemental cobalt species. Gold-cobalt nanoparticles formed by solvothermolysis showed magnetic response despite residual carbon monoxide ligands. Gold-cobalt nanocomposites formed by thermolysis in film had organization from the polymer, but were not magnetic.
Description	xi, 195 leaves : ill. (some col.) 28 cm.
Format	application/pdf
Advisor	Robert B. Grubbs
Subject	Block copolymers. Nanostructured materials -- Synthesis. Metallic composites -- Synthesis.
College	Dartmouth College -- Department of Chemistry.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Copyright	All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means without permission in writing from the author.
DOI	http://dx.doi.org/10.1349/ddlp.133

Title	Page 1
Format	application/pdf
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Full Text	SYNTHESIS OF MULTIMETALLIC NANOCOMPOSITE MATERIALS UTILIZING BLOCK COPOLYMERS A Thesis Submitted to the Faculty in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry by Laura B. Sessions DARTMOUTH COLLEGE Hanover, New Hampshire October 20, 2006 ____________________________ Charles K. Barlowe, Ph.D. Dean of Graduate Studies Examining Committee: ________________________________ Professor Robert B. Grubbs (chair) ________________________________ Professor Jane E.G. Lipson ________________________________ Professor Robert Ditchfield ________________________________ Professor Thomas A. Spencer ________________________________ Professor Todd Emrick

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