Preparation of mesophases

Materials used in the activation with KOH include high volatile bituminous coal C, coal semi-coke CS, pitch mesophase PM, pitch semicoke PS and commercial activated carbon AC. The semi-cokes CS and PS were produced by the heat treatment of corresponding parent materials at 520°C with a heating rate of 5°C/min and 2 hours soaking time. The preparation of mesophase PM comprised the soaking of coal-tar pitch at 450°C for 7 h with a continuous stirring. All the treatments were performed under argon in a vertical Pyrex retort of 45 mm diameter. 

Summary of Known Methods of Ereparation of Mesophase. At the time of writing, it appears that a major objective of research into the chemistry of mesophase formation is to obtain mesophase at as low a temperature as possible and to have a soluble mesophase, e.g. in 1,2,4 trichlorobenzene (112). The applications of such mesophase(s) must be in the production of graphitizable pitch fibres. However, this direction of research could have applications in many other areas of carbon/graphite production. Therefore it is appropriate, now, to make a list of known methods of preparation of mesophase (113). 

Mesophase is susceptible to chemical reactions other than those induced by pyrolysis. Modifications to enhance fusibility or solubility for easier spinning (see Preparation of Mesophase Pitch) and to induce thermosetting for carbonization without deformation are both practical steps in carbon fiber manufacture. 

In those days, pitch chemistry had not advanced sufficiently to understand fundamentally the foregoing phenomena. The preparation of mesophase pitch with low softening point (the so-called "soft mesophase pitch") was based on direct experiment. Nevertheless through extensive and serious efforts, it became possible to prepare soft mesophase pitches from naphtha tars, decant oils from fluidized catalytic crackers (FCC), atmospheric-reduced crude oils, and other pitch-like materials. A typical example of these preparation procedures is the following. A purified FCC or naphtha pitch is heated at 400°C for one hour under methane to convert the pitch to a mesophase content of 23.6% (27,28). The mesophase separated by sedimentation has a softening point of 226°C it is spun at 320°C, and the fiber is stabilized in air and finally carbonized by rapid heating at 100 to 1600°C/min (29). 

Preparation of Mesophases. Lipopeptides are dissolved in a small excess of water and, when total homogeneity is achieved, the desired concentration is obtained by slow evaporation at room temperature. Then the sample is left at room temperature in tight cells to reach equilibrium. 

Reprinted with permission from Hornby J, Kearsey HA, Carbon fibres from pitch precursors 2. The preparation of mesophase pitches suitable for spinning into fibres, AERE Harwell report AERE-M 3029, Oct 1979. Copyright 1979, AEA Technology pic. 

Mochida I, Shimizu K, Korai Y, Otsuka H, Sakai Y, Fujiyama S. Preparation of mesophase pitch from aromatic hydrocarbons by aid of HF/BF3. Carbon 1990 28(2-3) 311-319. 

Scheme 6 Steps involved in the preparation of mesophase pitch by the hydrogenation method...

Bose, F., Ayral, A., Albouy, P.A., Datas, L. and Guizard, C. (2004) Mesostructure of anatase thin films prepared by mesophase templating. Chemistry of Materials, 16 (11), 2208-2214. 

Advances in the chemistry of [M(CN)5L]" complexes, for M = Fe, Ru, and Os, have been reviewed.There has been rather little activity in the preparation of novel complexes, but considerable activity in studying the properties, especially solvatochromism and various aspects of kinetics of substitution, of known complexes. However there has been an attempted preparation of [Fe(CN)5(Ci2H25NH2)], in the hope of generating micelles or lyotropic liquid crystals. This preparation appeared to yield [Fe(CN)4(H20)(Ci2H25NH2)], whose alkali metal salts gave a hexagonal mesophase in water, but were also readily hydrolyzed to [Fe(CN)4(H20)2] . Heterobinuclear complexes of the form [(NC)5FeL ML 5] " " have been much studied, especially in relation to intramolecular electron transfer (see Section 5.4.2.2.5). 

The preparation of a cubic phase with supramolecular chirality was achieved using a branched folic acid derivative incorporating glutamic acid residues (Fig. 11) as the source of chirality [93]. The pterin rings of folic acid residues are able to form a cyclic tetramer as a result of two hydrogen bonds between the components. Depending on the number of carbon atoms in the alkyl substituents, the compounds form columnar phases over a wide temperature range, and for 8 and 9 form cubic phases at temperatures above 130 °C. Addition of sodium triflate stabilises the cubic phase for 7, and the salt is incorporated into the other mesophases. It was implied that the cation resides between stacked tetramers. Supramolecular chirality is expressed for both the columnar and the cubic phases, as revealed by vari-... 

The technology of mesophase-pitch-based carbon fiber has stimulated the rapid development of the chemistry of mesophase behavior and preparation. The carbonization schemes and mechanisms leading to optical anisotropy via the mesophase, the control of carbonization with emphasis on the preparation of spinnable mesophase, and the mesophase transition and reactivity in relation to the structure of its constituent molecules are summarized in this paper. 

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