The molecular structures comprising catalytically polymerized pyrene pitch Original Research Article

Key molecular species present in a model pyrene pitch catalytically polymerized (using AlCl3) from pure pyrene have been unambiguously identified. Packed-column, dense-gas extraction, using supercritical toluene as the solvent, was used to fractionate the pitch into monomer- and dimer-rich cuts. The resultant fractions were then analyzed for molecular-structure information via matrix-assisted, laser desorption/ionization (MALDI) mass spectrometry and by high performance liquid chromatography (HPLC) with UV–vis detection. Results indicate that only one of the possible isomers of pyrene dimer, that is, 1.14,7.8-dibenzoperopyrene, is present. In addition, mono-, di-, and tri-methylated pyrenes, which are completely absent in the starting pyrene, are present in the pyrene pitch in small but nontrivial (i.e., several per cent) quantities. Furthermore, the purity of the starting pyrene has no discernable impact on the relative amounts of alkylated pyrene species that are produced. A portion of the pyrene dimers, trimers, and tetramers are similarly alkylated.