Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thermal diffusivity (D), measuring how fast heat propagates in a medium, is an important quantity in heat conduction. For a medium with great thermal diffusivity, it will reach thermal equilibrium in shorter time. In the field of solid state materials, thermal diffusivity can give information about the quality and morphology of solid, since D is very sensitive to microstructures. However, studies on the thermal diffusion of organic semiconductors are very scarce. In this thesis, the thermal diffusion of different classes of photovoltaic polymers and their blends with molecular electron acceptors were studied by scanning photothermal deflection (SPD) technique. The reliability of the technique was confirmed by the good matching between the SPD derived experimental D values and the nominal D values of different reference materials obtained from literatures. To illustrate that determination of thermal diffusivity is a possible method for studying microscopic properties of organic photovoltaic materials, SPD technique was applied to various films of photovoltaic polymers with different crystallinities. It is observed that photovoltaic polymers always possess small D values in the range of 0.3mm2/s to 2.3mm2/s. It is also discovered that photovoltaic polymers with more planar molecular structure, stronger π-π stacking and higher crystallinity would possess larger D values. When photovoltaic polymers are blended with small molecular acceptors bulk heterojunctions (BHJs), the thermal diffusivity is always reduced due to disrupted polycrystalline structure and increase probability of intermolecular phonon transport. However, for all-polymer BHJs with polymeric acceptor, the reduction in thermal diffusivity can be moderate as the proportion of ultrafast intramolecular phonon transport is SPD technique was also applied to PBDB-T:(ITIC-M+N2200) ternary BHJs with different ITIC-M to N2200 weight ratio. The thermal diffusivity of the ternary blend increases with the weight percentage of N2200 polymeric acceptor. It is observed that PBDB:(ITIC-M+N2200) ternary photovoltaic devices with enhanced thermal diffusion can possess enhanced photostability. Such enhancement in photostability is attributed to the reduced heat trapping at the area being illuminated due to the improved thermal diffusion.

No description available.

by Ng Yee Kong. / Chinese title in romanization: Mo chong ji guang ruo fu she fa ce liang gao zhu wu bo mo di dao wen xi shu. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1987. / Bibliography: leaves 148-150.

Typescript (photocopy) / 167 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Physics, University of Adelaide, 1978

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 121-129).

Thesis (Ph.D.) Dept. pf Physics, University of Adelaide, 1978. / Typescript (photocopy).

Many properties of polymers can be affected by dissolving gases and supercritical fluids at high temperatures and pressures. Solubility and diffusivity are crucial parameters in polymer processing applications that indicates the content of gases and supercritical fluids in a polymer. Hence, different devices for measuring solubility and diffusivity have been researched, but most of the devices used today are very complex, expensive, and requires long experiment time. In this final thesis, the feasibility of fiber optic sensors as measurement devices for solubility and diffusivity of gas/SCF in polymers have been investigated. Many of the polymers used in polymer processing have high refractive index, from 1.40 to 1.60. However, most of the refractive index sensors based on fiber optics only operate in refractive index ranges of 1 to 1.44 because once the surrounding refractive index becomes greater than that of cladding, the total internal reflection is lost and only small portion of the light propagation occurs. This final thesis first reviews the current methods to measure solubility and diffusivity of gases and supercritical fluids in polymers. In addition, different types of fiber optics sensors used for sensing the refractive index are reviewed. Then, the thesis presents cost efficient, but effective fiber optic refractive index sensors, which are the silver nanoparticle coated LPG sensor, uncoated PCF MZI sensor, silver nanoparticle PCF MZI sensor, and the transmission intensity based gap sensor, to sense the surrounding refractive index in the region greater than the cladding, for the future application of solubility and diffusivity measurement. Moreover, future works that would help in sensing solubility and diffusivity of gas in polymers are also proposed. / Graduate

No description available.

Two different types of rhizomorphs were produced by A. luteobubalina in vitro conditions - aerial and submerged. They differed in growth rate, amount of mucilage, extent of peripheral hyphae, degree of pigmentation and in the structure of inner cortex. Otherwise they had a similar internal structure comprising 4 radial zones, namely, peripheral hyphae, outer cortex, inner cortex and medulla. Two membrane permeant symplastic fluorescent tracers, carboxy-DFFDA and CMAC which ultimately sequestered in vacuoles, behaved in a similar fashion in aerial and submerged rhizomorphs regardless of whether pigment was present in the outer cortical cell walls or in the extracellular material. Rhizomorphs appeared to be mostly impermeable to these probes with exception of a few fluorescent patches that potentially connected peripheral hyphae to inner cortical cells. In contrast, the apoplastic tracer HPTS which was applied to fresh material and its localisation determined in semi-thin (dry) sections following anhydrous freeze substitution appeared to be impeded by the pigmentation in cell walls and/or the extracellular material in the outer cortical zone. Structures identified as air pores arose directly from the mycelium and grew upwards into the air. A cluster of rhizomorph apices is initiated immediately beneath the air pores. As air pores elongated they differentiated into a cylindrical structure. Mature air pores became pigmented as did also the surface mycelium of the colony. The pigmented surface layer extended into the base of air pores, where it was elevated into a mound by tissue inside the base of the air pore. Beneath the pigmented surface layer there was a region of loose hyphae with extensive gas space between them. This gas space extended into the base of the air pore and was continuous with the central gas canal of rhizomorphs. Oxygen is conducted through the air pores and their associated rhizomorph gas canals into the oxygen electrode chamber with a conductivity averaging 679??68x10-12 m3s-1. The time averaged oxygen concentration data from the oxygen electrode chamber were used to compare three different air pore diffusion models. It was found that the widely used pseudo-steady-state model overestimated the oxygen conductivity. Finally, a model developed on the basis of fundamental transport equations was used to calculate oxygen diffusivities. This model gave a better comparison with the experimental data.