82
J. Godzwon et al. / Thermochimica Acta 531 (2012) 75–82
For the smectic
I
phase identification terphtal-bis-(4-
point. The composition at this point is constant and weakly
oscillates around a value of 0.2.
2. With standard II
(d) Investigated diagrams confirm presence of the SmI in octyl,
nonyl, decyl and dodecyl derivatives.
(e) Vitreous properties of lowest mesophases in the broad
concentrations range are observed.
butylaniline) was used as a standard II [1,32,33]. The phase
diagrams, which are shown in Fig. 6, confirm the presence of
smectic C and smectic I phases in the investigated derivatives.
Temperatures of phase transitions occurring in standard II are
much higher than in the investigated compounds. Therefore, the
obtained diagrams are less readable, with narrow and long areas of
mesophases. Because of the clarity invariant lines have been also
reduced to the points. However, the areas of the smectic C and I
phases are easy recognizable.
Additionally, on the discussed diagrams nematic and smectic
A phases are separated by a narrow line. The influence of the
alkyl chain length on the stabilization of smectic A phase and the
are vitreous transitions.
Typical textures of the investigated mixtures of 4-
II are shown in Fig. 7. Fig. 7a presents texture of nematic phase,
which appears as a round area with schlieren texture. The round
area increases on cooling. The black area is connected with a
homeotropic orientation of molecules. Fig. 7b presents a fan-
shaped texture, which is typical for smectic A mesophase. Still the
black areas of a spontaneous homeotropic orientation of molecules
are observed. On Fig. 7c fan texture of smectic A is replaced by
broken fan texture, which is typical for smectic C mesophase. In
place of the black areas observed on Fig. 7b is now a schlieren
texture very typical for smectic C phase. The SmC–SmI phase
transition proceeded in a very characteristic way (Fig. 7d). Broken
fan texture areas of smectic C change into polygonal texture,
typical of smectic I phase. Fig. 7e and f shows textures of the
smectic F and G mesophases, which are ambiguous.
(f) The increase of the alkyl chain length has the influence on
the stabilization of smectic A phase and the destabilization
of the nematic phase. The increase of the alkyl chain length
also destabilizes the G mesophase.
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Investigated compounds have following phases: nematic
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(c) The investigated compounds do not form solid solutions
with the standard I. All mixtures show a simple eutectic