Comparison of mesophase pitches derived from C8 and C9 aromatic hydrocarbons

Mesophase pitch prepared from C8 aromatic hydrocarbons through CH₂ coupling and successive heat treatment were characterized by NMR, IR, FD-Mass, and X-ray diffractometer to compare with C9 aromatic hydrocarbon-derived mesophase pitches. Two kinds of pitches showed very similar molecule structure with cata-condensed type. The C9 pitches carried much higher contents of methyl group and a larger number of aromatic rings than the C8 pitches, reflecting higher reactivity of the starting hydrocarbons. The number of methyl groups was found to have an influence on the properties of the pitch. The greater number of methyl groups in C9 pitches lowered the softening point, increased the stacking of mesogen molecules, and improved spinning and stabilization properties of the pitch, giving better tensile modulus of the resultant carbon fiber. Such a significant role of methyl groups in the mesogen molecules is common to those observed with naphthalene and methylnaphthalene-derived mesophase pitches.