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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
261

Multi-step self-assembly route to three-dimensional block copolymer-semiconducting nanoparticle photonic arrays with structural hierarchy

Yusuf, Huda 24 November 2009 (has links)
A new multi-step self-assembly route to polymer-semiconducting nanoparticle photonic structures is described. The multi-step self-assembly strategy targets complex hierarchical structures in which organization of cadmium sulfide (CdS) nanoparticles on progressively longer length scales is introduced via a series of three self-assembly steps. each involving building blocks of increasing structural complexity. Each self assembly step can be described as follows: 1) SA1: self-assembly of PS-b-PAA to form block ionomer reverse micelles, followed by synthesis of a single CdS semiconducting nanoparticle in each core, forming the hybrid building blocks PS-CdS: 2) SA2: self-assembly of blends of PS-CdS and PS-b-PAA stabilizing chains in DMF/water mixtures by addition of water to form spherical nanoparticle assemblies, termed large compound micelles (LCMs); 3) SA3: self-assembly of LCMs into ordered close packed arrays by slow water evaporation. The kinetic freezing of building blocks at each stage offers the potential for unique control of nanoparticle self-assembly step since each step is "locked in", allowing structural features determined by the subsequent step to be independently tuned through a new set of experimental variables. Chapter 2 and 3 of this thesis investigate aspects of size and polydispersity control of spherical nanoparticle assemblies in the SA2 self-assembly step. Chapter 4 demonstrates that LCMs can be further assembled (SA3 step) to form three-dimensional hierarchical arrays.
262

Random controlled free radical copolymerization of acrylic acidstyrene and tert-butyl acrylatestyrene mixtures using nitroxide mediators

Lessard, Benoît H., 1985- January 2008 (has links)
Controlled free radical polymerization facilitates the production of polymers with highly defined microstructures like traditional ionic polymerization; but in contrast allows for previously unattainable monomer combinations such as acrylic acid in its non-protected form. Incorporation of acrylic acid into styrene was done by random copolymerization of acrylic acid (directly and in its protected form as tert-butyl acrylate) with styrene. Styrene/tert-butyl acrylate (S/t-BuA) as well as styrene/acrylic acid (S/AA) mixtures were copolymerized to form tapered or gradient copolymers. Using an alkoxyamine unimolecular initiator, 2-[N- tert-butyl-2,2-(dimethylpropyl)aminooxy] propionic acid (BlocBuilder RTM), along with additional free nitroxide (SG1), the effect of acid protection on polymerization kinetics and copolymer composition was determined. Adding 4.5 mol% SG1/BlocBuilderRTM greatly improved the control of S/t-BuA copolymerization with low polydispersities (1.14-1.22) whereas the S/AA required higher levels of SG1 to produce polymers with low polydispersities that were comparatively still broader compared to the S/t-BuA system (polydispersities ∼ 1.3-1.4 at 9 mol% SG1/BlocBuilderRTM). S/AA copolymerization required higher SG1 concentrations to compensate for degradation of SG1 by attack from the acrylic acid monomer.
263

Synthesis of Arborescent Amphiphilic Copolymers

Alzahrany, Yahya 01 January 2013 (has links)
Living anionic polymerization techniques were applied to the synthesis of arborescent (dendritic) well-defined graft polymers having core-shell morphologies, with a hydrophobic core and a hydrophilic shell. Cycles of polystyrene substrate acetylation and anionic grafting yielded successive generations of arborescent polystyrenes. The anionic polymerization of styrene with sec-butyllithium provided polystyryllithium serving as side chains. These were coupled with a linear acetylated polystyrene substrate to obtain a generation zero (G0) arborescent polymer. An analogous G0 hydroxyl-functionalized polystyrene substrate with hydroxyl end groups was also obtained by a variation of the same technique, using a bifunctional organolithium initiator containing a hydroxyl functionality protected by a silyl ether group to generate the polystyrene side chains. These were coupled with the linear acetylated polystyrene substrate and subjected to a deprotection reaction to give the G0 polymer functionalized with hydroxyl groups at the chain ends. A similar procedure was used to generate a hydroxyl-functionalized arborescent G1 polymer from the corresponding G0 acetylated polystyrene substrate. The growth of polyglycidol chain segments was attempted from the hydroxyl-functionalized cores, to form a hydrophilic shell around the hydrophobic cores, but led to extensive degradation. A click reaction was also developed to synthesize the amphiphilic copolymers and was much more successful. In this case alkyne-functionalized arborescent polystyrene substrates, obtained by a modification of the hydroxyl-functionalized arborescent polystyrenes, were coupled with azide-functionalized polyglycidol side chains.
264

Synthesis Of Thiophene Capped Polytetrahydrofuran Conducting Copolymers

Unur, Ece 01 January 2003 (has links) (PDF)
Living polytetrahydrofuran (PTHF) was terminated with sodium thiophenemethonate to yield a polymer with thiophene groups at one (PTHF1) and both ends (PTHF2). Copolymerizations of PTHF1 and PTHF2 insulating polymers with pyrrole and thiophene were achieved in water-p-toluene sulfonic acid (PTSA) and acetonitrile (AN)-tetrabutylammonium tetrafluoroborate (TBAFB) solvent-electrolyte couples via constant potential electrolysis. Characterization of the samples were performed by Nuclear Magnetic Resonance Spectroscopy (NMR), cyclic voltammetry (CV), Fourier Transform Infrared Spectroscopy (FT-IR), Thermal Analyses (TGA), (DSC) and Scanning Electron Microscopy (SEM). Electrical conductivities were measured by four-probe technique. PTHF1/PTh and PTHF2/PTh films which were deposited on ITO-glass in dichloromethane-TBAFB solvent-electrolyte couple found out to be anodically coloring copolymers that electrochemically switch between an oxidized blue and reduced red state exhibiting electrochromic behavior. Spectroelectrochemical Analysis (SEC) was run in UV-VIS region to reach a better understanding of the band structures of PTHF1/PTh and PTHF2/PTh electrochromic copolymers. Optoelectrochemical analyses were introduced as a new method for the characterization of copolymers.
265

Poly(N-isopropylacrylamide) at the air/water interface /

Zhang, Ju. January 1998 (has links)
Thesis (Ph.D.) -- McMaster University, 1999. / Includes bibliographical references. Also available via World Wide Web.
266

Nanoscale investigation of polarization interaction and polarization switching in ferroelectric P(VDF-TrFE) copolymer samples

Kim, Jihee. January 1900 (has links)
Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed July 22, 2008). PDF text: ix, 169 p. : ill. (some col.) ; 8 Mb. UMI publication number: AAT 3299685. Includes bibliographical references. Also available in microfilm and microfiche formats.
267

Supramolecular block and random copolymers in multifunctional assemblies

Burd, Caroline Glenn January 2008 (has links)
Thesis (Ph.D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Marcus Weck; Committee Member: Bunz, Uwe; Committee Member: Collard, David; Committee Member: Jones, Christopher; Committee Member: Payne, Christine
268

Molecular dynamics simulations of polymer nanocomposites containing polyhedral oligomeric silsesquioxanes

Patel, Reena R. January 2004 (has links)
Thesis (M.S.)--Mississippi State University. Department of Computational Engineering. / Title from title screen. Includes bibliographical references.
269

Orthogonal functionalization strategies in polymeric materials

Yang, Si Kyung. January 2009 (has links)
Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2010. / Committee Chair: Weck, Marcus; Committee Member: Breedveld, Victor; Committee Member: Fahrni, Christoph; Committee Member: Kelly, Wendy; Committee Member: Lyon, L. Andrew. Part of the SMARTech Electronic Thesis and Dissertation Collection.
270

Thermodynamic and kinetic control of charged, amphiphilic triblock copolymer assembly via interaction with organic counterions in solvent mixtures

Cui, Honggang. January 2007 (has links)
Thesis (Ph. D.)--University of Delaware, 2007. / Principal faculty advisor: Darrin J. Pochan, Dept. of Materials Science & Engineering. Includes bibliographical references.

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