A series of evolving frontier energy levels and gaps sulfone-containing thienylenevinylene-based conjugated copolymers have been synthesized via the Horner-Emmons reactions between 2,5-bisdiethoxyphosphorylmethyl-3,4-dihexyl-1,1-dioxothiophene and a series of different donor type dialdehyde comonomers. The resulting polymers (SF-PTVs) contain alternating donor (benzene or thiophene ring with/without alkoxy substituents) and acceptor (1,1-dioxothiophene) units. A range of HOMO/LUMO levels and energy gaps (between 1.0 and 2.0 eV) were achieved in these new polymers. The use of oxidized thiophene moiety brings about 0.3 eV in reduction of energy gap. Computational study on the model oligomers of P(C6OTV-SFTV) and related structures reveals that the reduction is mainly due to the removal of aromaticity of the thiophene. The donor-acceptor interaction is also responsible for about one-third or less of the energy gap reduction. Theses polymers have very good thermal stability (dynamically, 258 °C or higher), and their decomposition starts with loss of mass as in contrast to regular PTVs which decompose initially by cross-linking.
We have found that R6G laser dye in a concentration of 0.1 g l −1 mixed with a solution of aggregated silver nanoparticles exhibits a new emission band with a maximum at 612 nm. This band does not exist in pure dye of comparable concentration or in a mixture of dye with a solution of single silver nanoparticles. A qualitatively similar red-shifted emission band is observed in pure R6G dye at very high concentration (3.8 or 16.7 g l −1). In both cases, no changes occur to the shapes of the absorption spectra of the dye. We explain the observed spectral changes in terms of J-aggregates of R6G molecules whose formation is probable in the presence of Ag aggregates with a complicated surface structure and is much less likely in the case of adsorption of dye molecules on single Ag nanoparticles. Alternatively, many features observed in the experiment can be explained by an enhancement of the rates of spontaneous radiative transitions in the proximity of metallic particles, which is due to a modification of the local density of electromagnetic modes in the vicinity of metal surfaces at energies resonant with surface plasmon resonances.
Abstract. Ground state and excitation energies of poly(3-methoxy-thiophene) (PMT) and poly(thienylene vinylene) (PTV) conjugated polymers are studied by first principles density functional theory (DFT). Two basic approaches of computational chemistry and physics are compared: time dependent DFT (TDDFT) of clusters and ab initio pseudopotentials within a standard DFT (PP-DFT) of infinite polymer chains. We demonstrate that series of excitation energies of PMT calculated by TDDFT with increased unit numbers converge well to the real experimentally measured energy gaps. Combination of TDDFT cluster method with PP-DFT approach for infinite chain provides single-gap quasiparticle correction value needed for optical calculations. Infinite chain model is used to calculate optical absorption of PTV.
The purpose of this chapter is to show how design-based research (DBR) methodologies can be implemented in technical programs. First, the authors provide a background of recent research in interdisciplinary education, Integrative Graduate Education Research Traineeship (IGERT) programs, and design-based research. Second, a brief summary the example case, a Pedagogy module which has been implemented with Materials Science and Materials Engineering students through an IGERT program, is discussed. The final portion of the chapter presents a new implementation model for DBR along with recommendations and strategies for interested faculty, department heads, or motivated graduate students to reform existing technical curricula using design-based research. The significance of the book chapter rests in the flexibility of this model to be adapted to any program, showing instructors the iterative process for developing a course to suit the needs of a department.
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