Crystal Structure and Smectic Orientation of a Mesogenic Compound

• Published in: Journal of macromolecular science. Physics 2004-11, Vol.43 (6), p.1263-1280
• Main Authors: Asano, Tsutomu, Kondo, Mitsuru, Natsume, Mikoto, Tsumagari, Noriko, Alam, Md. Mahay, Sawatari, Chie, Würflinger, Albert
• Format: Article
• Language: English
• Subjects: Aliphatic, non-condensed and condensed benzenic, and alicyclic compounds; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Experimental determinations of smectic, nematic, cholesteric, and other structures; Liquid crystals; Melt crystal method; Mesogenic compound; Organic compounds; Physics; Single crystal method; Smectic; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0022-2348; 1525-609X
• DOI: 10.1081/MB-200036816

The structure of the mesogenic compound 3-Cyanobenzyl-2,5-bis(4-n-octyloxy-benzoyl-oxy)benzoate (3CNBOB) was investigated by single and melt crystal methods. Using a single crystal of 3CNBOB at 20 °C, the unit cell structure was determined as triclinic with two molecules in a unit cell of dimensions: a = 8.792 Å, b = 11.760 Å, c = 19.121 Å, α = 96.61°, β = 90.56°, and γ = 90.28°. Three benzene rings of the compound exhibit π-π interactions in the crystalline form. The 3CNBOB showed a liquid crystalline state in the region of 82.9 to 101.5 °C. Melt crystallization was observed by in-situ x-ray diffraction using a temperature slope apparatus. A smectic phase appeared in the liquid crystalline region near the boundary to the crystalline phase. The smectic molecules showed spontaneous orientation aligned with their long axes parallel to the crystallizing plane. There were two crystalline states in the bulk material. The room-temperature crystalline form was the same as the one observed using the single crystal. The high-temperature crystalline state developed from the smectic state. During the smectic-crystalline transition, the packing became denser and the spontaneous orientation decreased.