SYNTHESIS AND CHARACTERIZATION OF MESOPHASE SPHERES FROM HYDROGENATED PYRENE THROUGH TWO-STAGE HEAT TREATMENT UNDER GAS FLOW.

Carbanaceous mesophase spheres were prepared from a hydropyrene pitch rather selectively through a two-stage process, the first and second of which were heat treatments at 430 degree C under vacuum and at 400 degree C under rapid nitrogen flow. Sheres were isolated by pyridine extraction and their structure and chemical composition were investigated by optical microscopy, scanning electron microscopy, solvent fractionation, and gel permeation chromatography. The spheres displayed Brooks-Taylor stacking and were found to contain a pyridine-insoluble but quinoline-soluble (PI-QS) fraction of condensed trimers, tetramers, and pentamers of pyrene units which may be anchored by the quinoline-insoluble fraction to be anisotropic in the sphere. Such chemical constituents may allow a reversible phase change in the mesophase pitch between isotropy and anisotropy. In contrast, the benzene-insoluble but pyridine-soluble fraction in the matrix was similar in its molecular size to that of PI-QS, although the higher hydrogen content of the former fraction may make it soluble in the matrix.