<p>Single-walled carbon nanotubes (SWNTs) are of special interest in current research due to their extraordinary mechanical, electronic and optical properties. Their unique structure, remarkable thermal and electrical conductivity, and high mechanical strength make SWNTs viable candidates for a wide range of device applications. However, pristine CNTs are not dispersible in most solvents, the main difficulties in CNT applications are related to their purification and solution-phase processing. In recent years, the supramolecular functionalization of SWNTs with conjugated polymers has received significant attention. Research within this field has been driven by the desire to find polymer structures that can selectively disperse certain nanotubes species with high efficiency.</p> <p>After a brief overview of the studies that are related to the investigation of the supramolecular interaction between various conjugated polymers and SWNTs (chapter 1), the synthesis of fluorene and thiophene-based conjugated polymers and their supramolecular complex formation properties with SWNTs are described (chapter 2, 3, 4, 5 and 6). In order to understand the effect that conjugated polymer structure has on formation of supramolecular complexes with SWNTs, various factors were investigated by: (1) altering the polymer backbone composition; (2) varying the polymer molecular weight; (3) introducing different solubilizing groups while the polymer backbone remained the same; (4) changing the polymer conformation. All of the resulting polymer-nanotube assemblies exhibit excellent solution stability in THF in the absence of excess unbound free polymer. The spectroscopic characterization of the polymer-SWNT complex materials indicated that the interaction between the conjugated polymers and SWNTs is strongly influenced by polymer structure.</p> <p>The interaction between a water soluble polythiophene derivative, poly[3-(3-N,N-diethylaminopropoxy)-thiophene] (PDAOT), and SWNTs is discussed in chapter 7. It is also demonstrated that the PDAOT-SWNT complexes form stable aqueous solutions that can be used for the fabrication of highly sensitive amperometric glucose biosensors.</p> / Doctor of Philosophy (PhD)

A theoretical model describing photophysics of π-conjugated aggregates, such as molecular crystals and polymer thin films, is developed. A Holstein-like Hamiltonian expressed with a multi-particle basis set is used to evaluate absorption and photoluminescence (PL) spectra. An analysis with line strength ratio proves to be a powerful diagnostic tool to obtain additional spectral signatures with which to distinguish H- vs. J-aggregation. For the H-aggregates absorption peak ratio, A0-0/A0-1, diminishes as the excitonic coupling increases. Also the PL peak ratio, I0-0/I0-1, is zero at T=0K with no disorder and the value increases as temperature and disorder increase. By contrast the J-aggregates show the opposite trends. Furthermore we will show the PL peak ratio provides a direct measurement of the exciton coherence length for a linear J-aggregate and could be expressed as I0-0/I0-1 = Ncoh/l2. We will also show that it is inversely proportional to square root of temperature (T-1/2). Applying our theory to the herringbone style oligoacene molecular crystals, we show the lowest singlet exciton states are highly influenced by charge transfer (CT) states and the well known energetic gap in two polarized absorption spectra, so called Davydov Splitting (DS), is a product of the interaction. We have successfully reproduced the DS for all three oligoacenes without any free parameters. Inspired by the CT contribution in oligoacene crystals, we further develop Wannier-Mott exciton model and apply to disorder-free polydiacetylene (PDA) quantum wires, which have been shown to be extremely emissive. We will show the quantum wire is a J-aggregate and we once again derive the peak ratio and the coherence size relation, I0-0/I0-1 = kNcoh/l2, where k is a prefactor close to unity. Typical photophysical properties of polymer p-stacks such as those occurring in P3HT films are well explained by the simple linear H-aggregate model. However several groups have started seeing more J-like behaviors amongst “improved” (less disordered) polymer films such as increased values of A0-0/A0-1 and I0-0/I0-1 and higher radiative rates. With the new perception of a single polymer chain being a J-aggregate, we apply our new theory to p-stack of polymer chains. We call this HJ-aggregate model since the interchain interaction induces H-aggregation. In the study we show a competition between intrachain and interchain interactions that leads to unique photophysical features. The new model is capable of explaining a wide range of polymer systems and most importantly the theory uncovers the mechanism of the improved polymer films; reducing disorder urges increasing intrachain reactions within each chain, thus enhancing more J-like spectral features. / Chemistry

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24585号 / 工博第5091号 / 新制||工||1975(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 関 修平, 教授 梶 弘典, 教授 SIVANIAH Easan / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

In this thesis, advanced spectroscopy methods are discussed and applied to gain understanding of the physical properties of organic conjugated molecules, II-VI thin film semiconductors, and vertical cavity surface emitting lasers (VCSEL). Experiments include single photon and two-photon excitation with lasers, with subsequent measurements of the absorption and photoluminescence, as well as photocurrent measurements using tungsten and xenon lamps, measuring the direct current and the alternating current of the devices. The materials are investigated in dissolved form (conjugated polymers), thin films (polymers, II-VI semiconductors), and complex layer structures (hybrid device, VCSEL). The experiments are analyzed and interpreted by newly developed or applied theories for two-photon saturation processes in semiconductors, bandgap shrinkage due to optically induced electron hole pairs, and the principle of detailed balance to describe the photoluminescence in thin film cadmium sulfide. / Ph. D.

Studies were conducted to investigate: 1) desaturation of dietary trans-vaccenic acid (TVA, trans11-18:1) to the cis9,trans11-18:2 isomer of conjugated linoleic acid (9/11CLA), 2) effects of two conjugated linoleic acid isomers [9/11CLA or trans10,cis12-18:2 (10/12CLA)] and TVA on enzyme activities and mRNA abundance for lipogenic enzymes, and 3) regulation of stearoyl-CoA desaturase (SCD) gene transcription. In the first study, lactating mice were fed 3% linoleic acid (LA), or 2% LA plus 1% stearic acid (SA), 1% TVA, or 1% CLA mixture. Dietary TVA enriched the 9/11CLA content of carcass, liver, and mammary tissue of lactating mice. A similar enhancement of 9/11CLA also was observed in liver, but not carcass, of suckling pups nursing TVA-fed dams. The CLA mixture decreased mammary acetyl-CoA carboxylase (ACC) activity compared with other treatments. However, total fatty acid content of mammary tissue was reduced only when compared with TVA. In the second experiment, lactating mice were fed 3% canola oil (OA), or 2% OA plus 1% SA, 1% TVA, 1% 9/11CLA, or 1% 10/12CLA. Dietary TVA, 9/11CLA, and 10/12CLA decreased mRNA abundance for ACC and fatty acid synthase (FAS) in mammary tissue, suggesting each had the potential to reduce de novo fatty acid synthesis. However, only the CLA isomers decreased ACC activity in mammary tissue and concentration of medium-chain fatty acids (MCFA = 12:0+14:0+16:0) in milk fat. The 10/12CLA isomer caused greater reductions in MCFA and milk fat percentage than the 9/11CLA, indicating that 10/12CLA is the primary CLA isomer affecting lipid metabolism in the mammary gland. Dietary TVA, 9/11CLA, or 10/12CLA decreased SCD enzyme activity and mRNA abundance in mammary tissue. In study 3, mouse (COMMA-D/MME) and bovine (Mac-T) mammary epithelial cells were transfected with the putative promoter (600 bp) of SCD gene. The 9/11CLA reduced SCD gene transcription in mouse cells, but not bovine cells. Transcription, however, was reduced in both cell lines by 10/12CLA, linoleic acid, and linolenic acid. Thus, reduced SCD transcription in response to the CLA isomers in mouse mammary cells in vitro may provide an explanation for reduced SCD enzyme activity and mRNA abundance in mammary tissue when lactating mice were fed either of the CLA isomers. In contrast, stearic acid, oleic acid, and TVA did not affect SCD transcription. Although TVA did not reduce SCD transcription in mouse mammary cells in vitro, it did reduce SCD enzyme activity and mRNA abundance in mammary tissue when fed to lactating mice. The results suggested TVA may influence SCD mRNA processing or stability in the nucleus after transcription. Despite the reduction in SCD mRNA and enzyme activity, however, substantial quantities of TVA were desaturated to the 9/11CLA isomer when TVA was fed to lactating mice in the first two studies. Thus, dietary TVA provides an alternate supply of the anticarcinogenic 9/11CLA isomer in tissues. / Ph. D.

Milk fat composition determines specific rheological, sensory and physicochemical properties of dairy products such as texture, melting point, flavor, color, oxidation rates, and viscosity. Previous studies have shown that milkfats containing higher levels of long chain polyunsaturated fatty acids have lower melting points and decreased solid fat contents which leads to softer-textured products. An increased risk of higher oxidation rates can be a disadvantage of high levels of polyunsaturated fatty acids. Three different milkfat compositions were obtained through dietary manipulation of cows: high oleic content, high linoleic content and control milkfat. Ice cream and butter were processed from the treated and control milks. Butter and ice cream samples then were analyzed to measure differences in fatty acid profiles and firmness. High-oleic and high-linoleic milkfat had lower concentrations of saturated fatty acids, such as C 16:0. Conjugated linoleic acid content was increased in the high-linoleic milkfat. High-oleic milkfat resulted in a softer butter. Ice cream samples were analyzed to measure differences in viscosity, melting point, oxidation rate and sensory perception. Significant differences (P<0.05) were found in the fatty acid profiles of milkfat, ice cream mix viscosity, peroxide values of ice cream after 3 to 5 months of storage, butter color, and butter firmness. Sensory analyses included a scooping test at -18°C to detect differences in texture. A difference test was conducted to determine oxidation flavor differences between the three ice cream treatments at extended storage times. No significant differences were found in the scooping test or the oxidation flavor difference. Manipulation of the cow's diet increased the total amount of unsaturated fatty acids. It also influenced firmness of butter and behavior of peroxide values during extended storage of high-linoleic ice cream. / Master of Science

<p dir="ltr">First, we aimed to incorporate stable tetracyanocyclopentadienide (TCCp) aromatic ani­ons into polynorbornene-based electrolytes, emphasizing controlled synthesis and properties through ring-opening metathesis polymerization (ROMP). Here, we first successfully incorporate a stable tetracyanocyclopentadienide (TCCp) aromatic anion into polynorbornene (PNb)-based elec­trolytes (PNb-TCCp) through ring-opening metathesis polymerization (ROMP) with controllable molecular weight and low polydispersity. PNb-TCCp shows a high ionic conductivity of 4.5 × 10^–5 S/cm in thin films. Due to its highly stable aromatic anion groups and favorable interactions with aromatic cations, it could improve thermal stability of doped conjugated polymers. Pairing with doped poly(3,4-ethylenedioxythiophene) (PEDOT) through salt metathesis, the generated poly ion complex PEDOT:PNb-TCCp retains its conductivity up to 180 °C.</p><p dir="ltr">Second, we aim to develop new photocatalysts for O-ATRP. We discovered a novel one-pot synthetic approach elu­cidates the formation of core-extended <i>N,N</i>′-disubstituted diaryl dihydrophenazine diradical dica­tions (DRDCs) via chemical oxidation. These DRDCs were reduced to their neutral state and found to have photocatalytic abilities, expanding the knowledge for O-ATRP photocatalysts.</p><p dir="ltr">Finally, we aim to understand the fundamental structure property relationship of the n-doped n-PBDF. The n-doped poly(benzodifurandione) (<b>n-PBDF</b>) is an n-type conducting polymer with characteristics such as high electrical conductivity, solution processability, and weathering stability. Here, we sys­tematically in­vestigate the structure property relationship on the impact of structural mod­ifications through aromatic substitution on the photophysical, electrical, and structural properties of <b>n-PBDF</b> and its oligomeric derivatives. We demonstrated that an electron donation group (methyl) raised the highest occupied molecular orbital energy level (+0.15 eV), while electron withdrawing halogens (Br and Cl) decreased the lowest unoccupied molecular orbital energy level (−0.12 eV and −0.13 eV, respectively) in the polymers. Additionally, in the both the undoped and doped oligo­meric systems, these substitutions introduce large torsion angles (<i>θ </i>> 17°), causing the material to twist significantly. Moreover, the methyl substituted polymer,<b> n-PBDF-Me</b>, was evaluated for its potential as a transparent organic conductor, due to its high optical transmittance (<i>T</i>₅₅₀> 93%). However, <b>n-PBDF-Me</b> films have significantly lower con­ductiv­ity than <b>n-PBDF</b> (0.40 S/cm vs 1330 S/cm) at similar thickness.</p>

No / The effects of a conjugated linoleic acid (CLA) mixture of single isomers (50:50, w/w, cis9,trans11:trans10,cis12) and the individual isomers on (a) the production of resting and calcium ionophore stimulated 14C-eicosanoids and (b) the incorporation of 14C-arachidonic acid (AA) into membrane phospholipids of human saphenous vein endothelial cells were investigated. The CLA mixture and the individual isomers were found to inhibit resting production of 14C-prostaglandin F2a by 50, 43 and 40%, respectively. A dose dependent inhibition of stimulated 14C-prostaglandins was observed with the CLA mixture (IC50 100 ¿M). The cis9,trans11 and trans10,cis12 (50 ¿M) isomers individually inhibited the overall production of stimulated 14C-prostaglandins (between 35 and 55% and 23 and 42%, respectively). When tested at a high concentration (100 ¿M), cis9,trans11 was found to inhibit eicosanoid production in contrast to trans10,cis12 that caused stimulation. The overall degree of 14C-AA incorporation into membrane phospholipids of the CLA (mixture and individual isomers) treated cells was found to be lower than that of control cells and the cis9,trans11 isomer was found to increase the incorporation of 14C-AA into phosphatidylcholine. Docosahexaenoic acid, eicosapentaenoic acid and linoleic acid did not alter the overall degree of incorporation of 14C-AA. The results of this study suggest that both isomers inhibit eicosanoid production, and although trans10,cis12 exhibits pro-inflammatory activity at high concentrations, the CLA mixture maintains its beneficial anti-inflammatory action that contributes to its anti-carcinogenic and anti-atherogenic properties.

The electrospinning technique is an attractive route for processing conjugated polymers (CPs) in a significant quantity for large-scale applications. However, the processing-structure-property relationship of the electrospinning process for CPs is not well understood. This dissertation provides a fundamental understanding regarding the structure development of CPs in electrospun fibers because of different processing conditions and relates that to fiber properties. Electrospinning was conducted for a mixture of polyethylene oxide (PEO) and poly(3-hexylthiophene) (P3HT) of three different molecular weights and two aging conditions: freshly prepared and 24 h aged spinning solutions. The aging of the spinning solution led to the self-assembly of P3HT chains, particularly with dominant H-aggregation for the higher molecular weight of P3HT. Those preexisting H-aggregates in the solution were retained and even increased in the fibers during electrospinning. Single fiber electrical conductivity, measured using a custom-built technique, has been found to increase with increasing molecular weight, particularly, a significant enhancement of that was observed for the fibers from the aged solution compared to the fibers obtained from the freshly prepared solution. Blending insulating polymers in CPs for electrospinning can hamper charge-carrier transfer, particularly when a large amount of insulating polymers is used for electrospinning. Thus, we adopted a coaxial electrospinning approach to avoid the blending of insulating components and to preserve the electrical properties of CPs. The coaxial fiber consisted of flexible polymers such as butyl rubber (BR), polymethylmethacrylate (PMMA), and PEO in the core and P3HT in the shell. BR in the core led to highly stretchable fibers. Further, P3HT in the shell facilitated the direct doping of the fiber without any post-treatment. The electrical conductivity of the doped fibers did not change significantly up to 400% strain and remained almost unchanged under cyclic loading, showing excellent mechanical reversibility. The general applicability of the spinning approach developed here has been demonstrated by successfully electrospinning donor-acceptor CP at the shell of the coaxial fibers. Our results provide new understandings linking the processing of CPs in fibers, the structural evolution of CPs in the fibers, and the corresponding electrical properties as a function of molecular weight, aging of solution, and mechanical loading.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25246号 / 工博第5205号 / 新制||工||1993(附属図書館) / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 田中 一生, 教授 大北 英生, 教授 大内 誠 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM