Chemistry Reference
In-Depth Information
ported in Refs. [65-68]. Each repetitive link is in certain amounts within
the polymer. All these copolymers are used as protective covers.
The thermotropic liquid-crystal copolyesters can be synthesized also
on the basis of
n
-oxybenzoic and 2,6-oxynaphthoic acid at presence of
catalysts (sodium and calcium acetates) [69, 70]. The catalyst sodium ac-
etate accelerates the process of synthesis. Calcium acetate accelerates the
process only at high concentration of the catalyst and influences on the
morphology of complex copolyesters.
The syntheses of copolymers of
n
-oxybenzoic acid with polyethylene-
terephthalate and other components are possible too [71-75]. It is estab-
lished that copolymers have two-phase nature: if polyethyleneterephthal-
ate is introduced into the reaction mix then copolymers of block-structure
are formed.
The properties of liquid-crystal copolyesters based on
n
-oxybenzoic
acid and oxynaphthoic acid (in various ratios and temperatures) are de-
scribed in Refs. [76-81]. It was shown therein that the plates from such
polymers formed by die-casting are highly anisotropic which results in
appearance of the layered structure. Those nematic liquid crystals had fer-
roelectric ordering. Following substances are characterized in Refs. [82-
85]: aromatic copolyesters of
n
-oxybenzoate/bisphenol A; those based on
n
-oxybenzoic acid, bisphenol and terephthalic acid; based on 40 molar
%
n
-oxybenzoic acid, 30 molar %
n
-hydroquinone and isophthalic acid;
and those based on
n
-oxybenzoic acid,
n
-hydroquinone and 2,6-naphtha-
lenedicarboxylic acid. The influence of temperature, warm-up time and
heating rate on the properties of copolyesters was studied: the glass-tran-
sition temperature was shown to increase with warm-up expanded. The
number of works is devoted to the study of the complex of physic-chem-
ical properties of liquid-crystal copolyesters based on
n
-oxybenzoic acid
and polyethyleneterephthalate [86-97]. It was established that mixes up
to 75% of liquid-crystal compound melt and solidify like pure polyethyl-
eneterephthalate. Copolyesters, containing less than 30% of
n
-oxybenzoic
acid, are in isotropic glassy state while copolyesters of higher concentra-
tion of the second compound are in liquid-crystal phase and can be char-
acterized by bigger electric inductivity, than in glassy state. This distinc-
tion in caused by the existence of differing orientational distribution of
major axes in relation to the direction of electric field in various structure
instances of copolyesters. The data of IR-spectroscopy reveal that
components of the mix interact in melt by means of reetherification reac-
