Chemistry Reference
In-Depth Information
II was determined in Ref. [138]. The distribution of triad sequences ap-
proximated to the characteristic one for statistical copolymer with in-
creasing of the exposure time.
The relaxation of liquid-crystal thermotropic polymethyleneterephtha-
loyl-bis(
n
-oxybenzoate) was studied in Ref. [139]: the β-relaxation oc-
curred at low temperatures while α-relaxation took place at temperatures
above 20
°
C (β-relaxation is associated with local motion of mesogenic
groups while α-relaxation is caused by the glassing in amorphous state). It
was established thin the presence of ordering both in crystals and in nem-
atic mesophase expanded relaxation.
So, the liquid-crystal nematic ordering is observed, predominantly, in
considered above polymeric systems containing links of terephthaloyl-
bis(
n
-oxybenzoic) acid [140] and combining features of both polymers
and liquid crystals. Such ordering can be characterized by the fact that
long axes of mesogenic groups are adjusted along some axis and the far
translational ordering in distribution of molecules and links is totally ab-
sent.
The analysis of references demonstrates that polyesters with links of
terephthaloyl-bis(
n
-oxybenzoic) acid can be characterized by the set of
high physic-mechanical and chemical properties.
That is why we have synthesized novel copolymers on the basis of
dichloranhydride of terephthaloyl-bis(
n
-oxybenzoic) acid and various aro-
matic oligoesters.
7.5
AROMATIC POLYARYLENESTERKETONES
The acceleration of technical progress, the broadening of assortment of
chemical production, the increment of the productivity of labor and quality
of items from plastics are to a great extent linked to synthesis, mastering and
application of new types of polymeric materials. New polymers of improved
resistance to air, heat form-stability, longevity appeared to meet the needs of
air and space technique. Filling and reinforcement can help to increase the
heat resistance on about 100 °C. Plastics enduring the burden in temperature
range 150-180 °С are called “perspective” while special plastics efficient
at 200 °C are named “exotic.”
The most promising heat-resistant plastics for hard challenges are poly-
sulfones. Today, the widely used aromatic polysulfones as constructional
