Abstract
Molecular alignment in methyl-naphthalene and naphthalene-derived mesophase pitch materials was studied at different levels of resolution by means of optical microscopy, X-ray, and TEM using the 002 lattice fringe technique, to determine the influence of different solidification procedures on the molecular alignment in the solidified pitches. Rapid resolidification procedures —quenching in liquid nitrogen or extraction —were found to reduce domain size and molecular alignment in the solidified pitch materials, whereas annealing followed by a slow cooling step produced better alignment, larger domains, or Brooks and Taylor type spheres, depending upon the composition of the pitch. Such rearrangement can be compared to a rate-controlled process such as recrystallization. Quite different molecular rearrangement behavior was found for naphthalene and methyl-naphthalene pitches, reflecting variations in their molecular stacking heights. The degree of liquid crystal alignment and the limitations of TEM in examining these types of structures are discussed.
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