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
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.