NEW STAR-SHAPED MESOGENS WITH THREE DIFFERENT ARMS ON A 1,3,5-BENZENE CORE Matthias Lehmann  Laboratoire de chimie des polyme `res, CP 206 = 1 Raluca I. Gearba and Dimitri A. Ivanov Laboratoire de physique des polyme `res, CP 223, Universite ´ Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium M. H. J. Koch European Molecular Biology Laboratory, Hamburg Outstation, EMBL c=o DESY, Notkestrasse 85, D-22603 Hamburg, Germany 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-benzoyl- benzoic acid derivatives, substituted with polar groups and n alkoxy chains (n ¼ 1–3), by using a combination of protecting group techniques and stoichio- metric 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 (–NO 2 ) enlarges the tempera- ture range of the liquid crystal phase. For all studied materials the diffracto- grams can be indexed according to a two-dimensional hexagonal lattice. The lattice parameters indicate that the flexible chains are interdigitated. Keywords: columnar liquid crystal; dipolar interaction; non-symmetric mesogen; star-shaped molecule We are grateful to the Communaute ´ Francaise de Belgique for its financial support (ARC n  00=05-257), to Prof. Herbert Meier for the availability of FD Mass and elemental analysis at the University of Mainz, to Prof. Yves Geerts for the generous support and helpful discussions. The synchrotron radiation work was supported by the European Union through the HCMP Access to Large Installation Project, Contract HPRI-CT-1999-00017 to the EMBL-Hamburg.  Corresponding author. E-mail: matthias.lehmann@ulb.ac.be 397=[1439] Mol. Cryst. Liq. Cryst., Vol. 411, pp. 397=[1439]–406=[1448], 2004 Copyright # Taylor & Francis Inc. ISSN: 1542-1406 print=1563-5287 online DOI: 10.1080=15421400490435422