Supermolecular liquid crystals with a six-armed cyclotriphosphazene core: from columnar to cubic phases.

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.