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Graduate / 0485

Graduate / 0485

Modern analytical techniques have been employed to investigate the nitration reaction of cellulose. The nitronium ion, NO(_2)(^+), is shown to be the important nitrating species of cellulose in the nitrating media employed. In mixes of high nitronium ion concentration, nitration at the cellulose surface is observed, by ESCA, to be extremely rapid, while in mixes of low nitronium ion concentration it is observed to be comparatively slow. It is shown that the degree of substitution (DOS) achieved at the fibre surface is equilibrium controlled. However, it is also shown that cellulose morphology plays an important role in determining the final bulk DOS achieved by nitration. The surface and bulk nitration of cellulose in dichloromethane/nitric acid mixes has been investigated by a variety of techniques. (^13)C solution state nmr has been employed to monitor the partial DOS established at the individual sites of the anhydroglucose residues. The substitution distribution patterns observed for materials in the DOS range 1.8 → 2.4 are very dependent on the nitrating media employed. Further, the differences in the substitution distribution pattern are reflected in the d(l0l) mean interchain spacing. A possible explanation for these differences is forwarded. The plasma etching of cellulose nitrate has been investigated as a function of DOS. The influence of sulphate ester residues on etch rate is also considered.

Universiẗat, Diss., 2001--Regensburg. / Erscheinungsjahr an der Haupttitelstelle: 2001.

学位授与大学：京都大学 ; 取得学位: 博士(工学) ; 学位授与年月日: 2007-11-26 ; 学位の種類: 新制・論文博士 ; 学位記番号: 論工博第3971号 ; 請求記号: 新制/工/1422 ; 整理番号: 25647 / Kyoto University (京都大学) / 0048 / 新制・論文博士 / 博士(工学) / 乙第12135号 / 論工博第3971号 / 新制||工||1422(附属図書館) / 25647 / UT51-2007-S505 / (主査)教授 吉田 潤一, 教授 檜山 爲次郎, 教授 杉野目 道紀 / 学位規則第4条第2項該当

One of the main objectives of this Thesis was to explore the use of thiophenes to synthesize several more complex aromatic systems. Thus starting from 2,4-dimethyl 5- amino-3-methylthiophene-2,4-dicarboxylate 115, the synthesis of the first cis-thia[ 13]annulene, 4-bromo-cis-9b,9c-dimethyl-9b,9c-dihydrophenyleno[1,9-bc]thiophene 116a, as well as the trans-isomer, 116b have been achieved in 11 steps. Introduction of a bromo-substituent at an early stage, facilitated rearrangement of the thiacyclophanes 119a and 119b to permit easier isolation of the product annulenes. Both the cis-thia[ 13]annulene 116a and the trans-thia[ 13]annulene 116b were found to be diatropic on the basis of their 1H NMR chemical shifts. Using thiophene dioxide 150 and 152 as key intermediates to generate multifunctional azulenes, the novel azulene containing thiacyclophane 105 has been synthesized in 9 steps. Even though this was not able to be converted to the [18]annulene 100, discovery of a new route to thiacyclophanes from thiolacetates was achieved. This has been tested successfully on a variety of other examples, including the unusual bis thiophene containing cyclophanes 194 and 195, as well as the unsymmetrical 191 which was subsequently converted to the dihydropyrene 236a and 236b. During the course of this work, we discovered a new mild method to electrophilically brominate reactive aromatics using NBS in [special characters omitted] at room temperature. This reagent was investigated for several thiophenes, azulenes and dihydropyrenes. The products from the latter were successfully coupled using Ni(0) catalysis to generate 28% of the first unsymmetrically connected dimer of DMDHP, 249, as well as 33% of the symmetrical dimer 102. Unlike 102, the bi-annulenyl 249 has a significant barrier to rotation, which is estimated as 11.0 kcal/mole from [special characters omitted] measurement, compared to a PCMODEL calculated barrier of 12 kcal/mole. This is the first measurement of the barrier to rotation in a 1,2'-binaphthyl type system. Electrophilic substitution in DMDHP using the diazonium salts 277 and 283 was also studied, and several novel cross-coupling products have been synthesized and isolated, such as 278 from 279 and 280. As well the very unusual isomeric quinones, 7-(10b, 10c-dimethyl-7-oxo- 2,7,10b, 10c-tetrahydro-2-pyrenyliden)-10b, 10c-dimethyl-2,7-10b, 10c-tetrahydro-2- pyrenone 263 and 264 have been successfully prepared by reacting 102 with NBS or PDC. Compounds 263 and 264 have highly extended conjugated systems. / Graduate

Atlas Copco is interested in investigating the friction in the top-hammer drilling tool threads thatcauses the steel to heat up, leading to a phase transformation and a softer steel in the threads. Theaim of this project is to find a steel alloy or surface finishing that will retain its hardness atelevated temperatures better than the presently used threads material. The solution is intended tobe used as a replacement material for the threads. The potential material is meant to combat thepremature breakdowns of the threads and thus minimizing the economical losses. To achieve ourproject goal, literature studies and an experimental parts were employed.Hardening methods are discussed thoroughly in the thesis, such as carbides/nitrides,precipitation, solid solution, grain size, and martensitic transformation. Alloying elements andtheir effects on steels properties were also discussed. C, Cr, Co, Mn, Mo, Ni, W, and V werefound to increase the steel's hardness at elevated temperature, high temperature strength andabrasion wear resistance.Nitration can be applied to most of the steels that Atlas Copco uses today, and will give a harder,and more wear resistant surface at elevated temperatures. A problem with nitration is that thenitrided layer is generally thinner than the martensitic hardening used today.Three tool steels samples (ASP 2030, ASP 2053 and ASP 2060) were acquired from Erasteel.These were used in the experimental part and compared to reference steels that Atlas Copcocurrently are using (R1-R6). The experiments were conducted in 400 and 600°C and the sampleswere tempered for 1, 10 and 100 hours before the hardness were measured with a Vickershardness test. The conclusion from the experiments was that ASP 2060 and ASP 2053 fromErasteel are the steels that have a much higher hardness at elevated temperature than the othersteels tested in the experiment. The results indicate that the tool steels will probably notexperience the same premature breakdown as the threads used today. R1 and ASP 2053 have thegreatest heat resistance.The suggested tool steels are all quite expensive, and to minimize the material needed only thethreads and not the rod can be in the new alloy. Lowering the cost could also be achieved byhardfacing where a layer of the new expensive alloy is welded onto a cheaper steel.

Graduate / 0485

Graduate / 0485