Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 158-165).

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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.

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.

No description available.

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.

Electrochemical and electrogenerated chemiluminescence properties of the BODIPY (boron dipyrromethene) dyes are presented. Some specific features of the BODIPY dyes are obtained and described in the current dissertation. Separation of around 1.0-1.2 V is noticed between two oxidation and reduction waves for one center which is very different from 0.5 V seen for the polycyclic hydrocarbons. Cathodic and anodic stability is shown to depend upon absence or presence of certain degree of substitution. Different ways of electrochemical dimerization are explored and compared with the chemical dimerization. Photophysical and electrochemical properties of monomer, chemically synthesized dimer, trimer and polymer are described and the characteristic features determined. / text