carbonaceous mesophase

https://doi.org/10.1351/goldbook.C00822
A liquid-crystalline state of
pitch
which shows the optical birefringence of disc-like (discotic) nematic liquid crystals. It can be formed as an intermediate phase during
thermolysis
(
pyrolysis
) of an
isotropic
molten
pitch
or by
precipitation
from
pitch
fractions prepared by selective
extraction
. Generally, the spherical
mesophase
precipitated from a pyrolysing
pitch
has the
Brooks and Taylor structure
. With continuous heat treatment the carbonaceous
mesophase
coalesces to a state of
bulk mesophase
before
solidification
to
green coke
with further loss of hydrogen or low-molecular-
weight
compounds.
Note:
In the formation of carbonaceous
mesophase
by
thermolysis
(
pyrolysis
) of
isotropic
molten
pitch
, the development of a
liquid-crystalline phase
is accompanied by simultaneous aromatic
polymerization
reactions. The reactivity of
pitch
with increasing heat treatment temperature and its thermosetting nature are responsible for the lack of a true reversible thermotropic
phase transition
for the
bulk mesophase
in most pitches. Due to its glass-like nature most of the liquid-crystalline characteristics are retained in the super-cooled solid state.
Source:
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 483 [Terms] [Paper]