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Supermolecular Liquid Crystals with a Six‐Armed Cyclotriphosphazene Core: From Columnar to Cubic Phases
Author(s) -
Jiménez J.,
Laguna A.,
Molter A. M.,
Serrano J. L.,
Barberá J.,
Oriol L.
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201002114
Subject(s) - mesophase , differential scanning calorimetry , crystallography , alkyl , circular dichroism , liquid crystal , materials science , mesogen , ether , phase (matter) , thermal stability , side chain , chemistry , organic chemistry , polymer , liquid crystalline , physics , optoelectronics , composite material , thermodynamics
New liquid crystals having a non‐conventional structure have been synthesised from a six‐armed cyclotriphosphazene core, [N 3 P 3 (OC 6 H 4 OH‐4) 6 ], which was condensed with polycatenar acids. Reactions were monitored by 31 P{ 1 H} and 1 H NMR spectroscopy and the chemical structure of the resulting materials was confirmed by different spectroscopic techniques and mass spectrometry (MALDI‐TOF). Results were in accordance with monodisperse, fully functionalised cyclotriphosphazenes. Thermal and mesomorphic properties were studied by optical microscopy, differential scanning calorimetry and X‐ray diffraction. All of the synthesised phosphazenes, substituted with benzyl ether chains, show a high thermal stability and exhibit mesomorphic properties, which depend on the number and type of alkyl terminal chains located at the periphery of the mesogens. Mesomorphic properties range from Col h for cph‐A1 and cph‐A2 to a cubic phase detected for cph‐A3 , which has the larger number of alkyl chains. Furthermore, helical order was detected on X‐ray data of cph‐A2 , which has chiral branched chains. Circular dichroism spectra of annealed films at mesophase temperature show a signal attributed to the chiral helical arrangement of the mesogenic chromophores.