Structural analysis of mesophase pitch with high-resolution, high-temperature 13C-NMR Original Research Article

The structural parameters of mesophase pitch with optical anisotropy have been successfully obtained by using high-temperature 13C-NMR spectroscopy. Well-resolved spectra were obtained from the mesophase pitch with the addition of pyrene, which played the role of solvent for a quinoline-insoluble rich mesophase pitch during NMR measurement at 573 K. The resolution of NMR spectra was improved due to the decline in viscosity, without any influence on the chemical shift for aliphatic carbons. Hydrogen distribution has been converted from the intensities of aliphatic carbon obtained by a high-temperature 13C-NMR spectrum. Average structural parameters of whole mesophase pitch were calculated with the distribution of hydrogen by using Brown-Ladner equations. Structural characteristics of the benzene-insoluble fraction in two kinds of mesophase pitch have been discussed as well as that of the benzene-soluble fraction and whole pitch.