Poly (para-phenylenevinylene) (PPV), and its derivatives such as poly [2-methoxy, 5-(2'-ethyl-hexoxy)-1,4-phenylene vinylene] (MEH-PPV), are typical conjugated polymers. In order to implement conjugated polymers into processable electronics technologies, we must first understand their complex photophysical properties as their efficiencies depend on the balance between exciton recombination and charge carrier formation. The inherent complexities of these materials arise from entanglement of the pi-electron system with disorder and nuclear motions of the polymer backbone. This disorder breaks the polymer chain into conformational subunits which can couple, giving rise to a set of delocalized states formed by Coulombic interactions between proximate subunits. Characteristics of PPVs include high quantum yields, non-mirror image absorption and fluorescence line shapes, and large apparent Stokes' shifts. These properties are discussed in the context of the relationships between polymer conformation, electronic structure, coupling, disorder and polymer photophysics. These important influences are often manifest in the dynamics of what happens after photoexcitation. In this work, we present 3-pulse photon echo peak shift (3PEPS) studies of conjugated polymers in both solution and film. To elucidate timescales characteristic of relaxation processes, we have simulated the 3PEPS data simultaneously with absorption and fluorescence, observing a rapid localization of the exciton in the initial ~ 20 fs. Additional contributions to the decay of the peakshift are discussed. We also present transient anisotropy data for PPV polymers and oligomers which is compared to dynamics simulation for isolated chains of PPVs. This work demonstrates the influence of microscopic structure on ultrafast dynamics. We show that relaxation between exciton states can lead to rapid depolarization of the anisotropy, even though the spatial extent of exciton migration may be small. Generally, the connection between conformation and electronic structure is a theme throughout this thesis.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed March 2, 2010). PDF text: xii, 86 p. : ill. (some col.) ; 9 Mb. UMI publication number: AAT 3386756. Includes bibliographical references. Also available in microfilm and microfiche formats.

Conjugated polymers are widely used and rapidly developed in practical polymer-based light-emitting electronic devices. Understanding the electrochemical reaction of conjugated polymer has become essential in the design and operation of devices such as electrochemical light-emitting diodes. In particular, we have studied the dynamics and kinetics of oxidation/reduction behavior of conjugated polymer single-molecules and nanoparticles in order to obtain the molecular level properties of deeply trapped holes in organic semiconductor devices. Theoretical calculations suggest the penetration of ions and solvent molecules effectively stabilizes the injected charges, which allows homogeneous charge distribution and further hole injection. The formation and decay of deep traps have been explored by changing the charging rate and duration. We found that the laser excitation significantly promotes the untrapping of deep holes. Electrogenerated chemiluminescence of single nanoparticles has been investigated to unravel the effects due to particle heterogeneity, which are masked in bulk electrochemical studies of nanoparticles. Bigger particles showed more intense light and longer duration time than smaller ones. Co-reactant, tripropylamine can facilitate the formation of electrogenerated chemiluminescence as well as alleviate the polymer oxidation and following irreversible electrochemical reaction. Electrochemically generated light waves from the conjugated polymer thin films have been visualized to obtain microscopic level understanding on the complex reaction mechanism. Electrochemical reaction occurs at local defects and propagates isotropically over macroscopic distances with a sharp wave front. The initially injected holes (oxidized polymers) drag counter-ions into the film, thereby induce a phase-transition-like swelling that enhances transport of ions and solvent and move forward the double layer and corresponding propagation of the wave. / text

No description available.

Fertility in human males is negatively correlated with obesity and diabetes mellitus (DM). Whether CLA influences obesity and DM associated infertility has not been studied. Seven-week-old male obese and DM-2 mice (db/db, n=40) were randomized to either an 8.5% (w/w) fat diet of a CLA isomer (0.4%, w/w) or a control diet for 6 weeks. Lean (n=10) mice were fed a control diet. The db/db mice fed a control diet displayed increased abnormal morphology, decreased sperm concentration. They also had decreased cst and cgt gene expression, despite increased seminolipid concentration, and decreased expression of genes involved in spermatogenesis compared to their lean counterparts. CLA isomers increased sperm number and normal sperm morphology, influenced seminolipid concentration, seminolipid enzyme gene expression and significantly increased Ccna1 gene expression. Seminolipid and genes of spermatogenesis appear to factor into DM and obesity induced reproductive dysfunction. Dietary CLA isomers appear to increase functionally viable sperm and thereby improve fertility.

Fertility in human males is negatively correlated with obesity and diabetes mellitus (DM). Whether CLA influences obesity and DM associated infertility has not been studied. Seven-week-old male obese and DM-2 mice (db/db, n=40) were randomized to either an 8.5% (w/w) fat diet of a CLA isomer (0.4%, w/w) or a control diet for 6 weeks. Lean (n=10) mice were fed a control diet. The db/db mice fed a control diet displayed increased abnormal morphology, decreased sperm concentration. They also had decreased cst and cgt gene expression, despite increased seminolipid concentration, and decreased expression of genes involved in spermatogenesis compared to their lean counterparts. CLA isomers increased sperm number and normal sperm morphology, influenced seminolipid concentration, seminolipid enzyme gene expression and significantly increased Ccna1 gene expression. Seminolipid and genes of spermatogenesis appear to factor into DM and obesity induced reproductive dysfunction. Dietary CLA isomers appear to increase functionally viable sperm and thereby improve fertility.

The synthesis of a series of poly(arylene vinylene)s via transition metals catalysed polycondensation with a view to producing well defined and clean samples for study , particularly for the incorporation of the material in light emitting devices has been described. Initially the McMurry reaction was applied in the synthesis of poly(4,4'-diphenylene diphenylvinylene). The reaction conditions have been optimised and relatively high molecular weight polymers with narrow molecular weight distributions were produced by fractionating the polymer. The feasibility of the McMurry reaction was established in the synthesis of related polymers; including poly(l,3-phenylene diphenylvinylene), poly(l,3-phenylene dimesitoylvinylene) and poly(4,4'-diphenylene-l,2-bis(pentafluorophenyl)vinylene). In other attempts the Yamamoto and Suzuki polycondensations were applied in the synthesis of structurally defined poly(arylene vinylene)s which could not be made via the route used earlier. Studies on UV-visible absorption, photoluminescence and electroluminescence properties of polymers produced were carried out and correlation between polymer structure and electro-optical properties of the polymer, particularly photoluminescence has been established.

Thesis (Ph.D.) - University of St Andrews, June 2008.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references. Also available in print.

Thesis (M.Sc.). / Written for the Dept. of Chemistry. Title from title page of PDF (viewed 2009/09/07). Includes bibliographical references.