par Lehmann, Matthias ;Gearba, Raluca Raluca R.I.;Ivanov, Dimitri ;Koch, Michel Hj
Référence Molecular crystals and liquid crystals, 411, page (397/[1439]-406/[1448])
Publication Publié, 2004
Article révisé par les pairs
Résumé : The convergent synthesis of new symmetrical and non-symmetrical star-shaped mesogens based on a phloroglucinol core is presented. Molecules with three different arms were derived via esterification of various 4-benzoylbenzoic acid derivatives, substituted with polar groups and n alkoxy chains (n = 1-3), by using a combination of protecting group techniques and stoichiometric reactions. The thermotropic properties were investigated by differential scanning calorimetry, polarised optical microscopy and synchrotron X-ray diffraction. It is found that molecules with more than seven lateral chains form mesophases. The presence of strong polar groups (-NO2) enlarges the tempemlure range of the liquid crystal phase. For all studied materials the diffractograms can be indexed according to a two-dimensional hexagonal lattice. The lattice parameters indicate that the flexible chains are interdigitated.