Disclinations in the Carbonaceous Mesophase

Abstract When the organic precursors to coke and manufactured graphite (petroleum and coal-tar pitches) are carbonized, large, flat, polynuclear aromatic molecules are formed by the reactions of aromatic polymerization. As the molecular weights approach 1500, usually near 450 C, the molecules condense to form a liquid crystal which has been termed the carbonaceous mesophase. The distinctive feature of the carbonaceous mesophase is the plate-like molecule, in contrast to the rod-like molecule of nematic liquid crystals. The carbonaceous mesophase thus appears to be a lamellar liquid crystal in which space is filled by plate-like molecules which may vary in size and shape but tend to pack in parallel arrays. These arrays are free to bend and twist as they trace out a lamelliform or Mobius morphology with topological discontinuities which bear similarities to the disclination structures found in conventional liquid crystals. Two types of lamellar disclinations may be conceived: layer-stacking disclinations r...

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