Iodine introduced into coal tar pitch (CTP) can drastically alter its reolo
gy and carbonization behavior. Here, the mechanism of interaction between i
odine and CTP has been investigated by using various spectroscopic methods
such as I-127-NMR, EPR and FT-IR. It is shown that some iodine molecules in
filtrated into the CTP and form charge transfer complexes with the relative
large aromatic components of the CTP. Hyperfine sublevel correlation spect
roscopy (HYSCORE) revealed the molecular size of cation radicals, which con
tain more than ten benzene rings, and the location of iodine anion that is
incorporated at ca. 0.3 nm from the aromatic cation radicals. The elemental
H/C ratio decreased and the viscosity of CTP increased with the density of
the charge-transfer complexes, which was also increased by the iodine trea
tment. These results strongly suggest that dehydrogenative polymerization o
f CTP occurs during the iodine treatment. The cation radicals in the charge
-transfer complexes accelerate the dehydrogenative polymerization and resul
t in a high carbon yield. (C) 2000 Elsevier Science Ltd. All rights reserve
d.