Mesomorphism of a banana mesogen: influence of a fluoro substituent in the central core

• Published in: Liquid crystals 2009-09, Vol.36 (9), p.977-987
• Main Authors: Rao, Nandiraju V.S., Deb, Rajdeep, Paul, Manoj Kr, Francis, Tuluri
• Format: Article
• Language: English
• Subjects: Banana shaped mesogens; Chemical compounds; Comparative analysis; Crystals; Electric fields; Experiments; Fluoro compounds; Molecules; phases; SmCP; Spontaneous polarization
• ISSN: 0267-8292; 1366-5855
• DOI: 10.1080/02678290903165979

The results of experiments with stable five-ring banana-shaped molecules consisting of laterally 4-fluoro substituted 1,3-phenylene ring as the central unit in Bis-[4-(4′-n-alkyloxybenzoyloxy)salicylidene]-phenylene-4-fluoro-1,3-diamines are presented. These compounds are thermally and hydrolytically stable due to intermolecular or intramolecular hydrogen bonding and exhibit SmCP A and low-temperature crystalline B X phases. The phases had been characterised by thermal microscopy and differential scanning calorimetry. A representative example has also been characterised by X-ray diffraction studies and electric field effects. The influence of a lateral fluoro substituent in the central core is clearly demonstrated with the induction of the SmCP A phase which is absent in the parent compound without the substituent. Further these compounds exhibit a large tilt angle. We also describe a comparison of phase behaviour with similar analogous compounds, taking the position of fluoro substitution, changes in the linking groups and the direction of the linking groups into consideration.