Thermotropic Phase Behavior of a Liquid-Crystalline Poly(ether ester) Derived from Hydroxydibenzoic Acid, 2-Methyl-1,3-propanediol and R-1,3-Butanediol
✍ Scribed by Juan P. Fernández-Blázquez; Antonio Bello; Ernesto Pérez
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 530 KB
- Volume
- 208
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
The thermotropic phase behavior of a liquid‐crystalline poly(ether ester) derived from 4′‐hydroxybiphenyl‐4‐carboxylic acid and two different spacer diols (2‐methyl‐1,3‐propanediol and R‐1,3‐butanediol) has been analyzed by differential scanning calorimetry, real time synchrotron X‐ray diffraction and solid‐state ^13^C NMR. It has been found that the polymer develops a smectic mesophase that presents order inside the layers. This mesophase has a slow rate of formation, in such a way that it is possible to obtain either an amorphous glass or a liquid‐crystalline glass. These two phases exhibit different and independent glass transition temperatures: 95 °C for the amorphous one and 85 °C for the mesophase. The diffractogram of this mesophase shows two clear diffractions in the wide‐angle region and a long spacing (of low intensity) in the small‐angle region. All those features are characteristic of a mesophase of intermediate order, presumably of the type SmI, in contrast to the low‐ordered SmC~alt~ mesophase reported for the racemic polymer. Thus, the chirality of the spacer, which provides structural regularity, makes easier the packing of the chains, so that a more ordered mesophase is obtained. In addition, both the solid‐state ^13^C NMR line shapes and the value of $T_{1\rho }^H $ are practically the same for the quenched and the annealed samples, indicating that the “ordered” phase obtained by annealing is not a three‐dimensional crystal, thus confirming its assignment as mesophase, with a considerable degree of conformational disorder.
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