X-ray investigation of new isomeric oxadiazoles

Oriano Francescangeli; L. A. Karamysheva; Sofia I. Torgova; A. Sparavigna; Alfredo Strigazzi

doi:10.1117/12.301271

1 January 1998 X-ray investigation of new isomeric oxadiazoles

Oriano Francescangeli, L. A. Karamysheva, Sofia I. Torgova, A. Sparavigna, Alfredo Strigazzi

Proceedings Volume 3319, Liquid Crystals: Chemistry and Structure; (1998) https://doi.org/10.1117/12.301271
Event: Liquid Crystals, 1997, Zakopane, Poland

Abstract

An x-ray investigation has been performed on five new 2,5- disubstituted 1,2,4-oxadiazoles with reversed structures containing 4-amylbiphenyl-, trans-4-amylcyclohexylphenyl- and 2-halophenyl- as substituents. The aim was to confirm the data about the phase sequence, obtained via polarizing microscopy and differential scanning calorimetry, and to measure the structural parameters. Through x-ray diffraction technique, all substances showed only the nematic mesophase. Moreover, it was proved that some enthalphy variations previously attributed to crystal-crystal transitions are in fact due either to the rearrangement of the lattice or to the coalescence of the grains. However, for some substances, a second crystalline from c' appeared at the melting point, on cooling from the isotropic phase. C' turned out to be different from the starting form C₁ of the sample, which had no thermal cycle before.

Citation Download Citation

Oriano Francescangeli, L. A. Karamysheva, Sofia I. Torgova, A. Sparavigna, and Alfredo Strigazzi "X-ray investigation of new isomeric oxadiazoles", Proc. SPIE 3319, Liquid Crystals: Chemistry and Structure, (1 January 1998); https://doi.org/10.1117/12.301271

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