Local structure of the B(4) phase studied by second harmonic generation and X-ray diffraction measurements

Texture observations, second harmonic generation (SHG) and X-ray diffraction measurements have been carried out in the B(4) phase of two classical bent-core liquid crystals. Several sample geometries have been used for the different techniques, including a well-aligned cell for the optical studies....

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Bibliographic Details
Published in:Journal of materials chemistry 2009-08, Vol.19 (29), p.5161-5166
Main Authors: Martinez-Perdiguero, J, Alonso, I, Folcia, C L, Etxebarria, J, Ortega, J
Format: Article
Language:English
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Summary:Texture observations, second harmonic generation (SHG) and X-ray diffraction measurements have been carried out in the B(4) phase of two classical bent-core liquid crystals. Several sample geometries have been used for the different techniques, including a well-aligned cell for the optical studies. An indexation of the whole diffraction diagram was performed on the basis of a three-dimensional lattice. A quantitative analysis of the X-ray data is also reported. The results are compatible with the well-known twist grain boundary (TGB) structure for the B(4) phase. However, within the smectic blocks the structure is monoclinic P2, implying an antiferroelectric in-layer arrangement of the molecules instead of the usually accepted ferroelectric. This antiferroelectric packing also explains the low efficiency of the B(4) phase for SHG.
ISSN:0959-9428
DOI:10.1039/b900832b