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Abstract
A series of guanidinium salts 1(C n ) m –4(C n ) m X bearing phenyl alkoxybenzoate cores have been synthesised and their mesomorphic properties have been investigated by polarising optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction experiments (small-angle X-ray scattering and wide-angle X-ray scattering). While compounds 1(C12)1 X and 3(C12)1 X with one alkoxy chain showed smectic A (SmA) phases irrespective of the counter ion, compounds 1(C12)2 OTf and 3(C12)2 OTf with two alkoxy chains displayed SmA phases and the corresponding chlorides 1(C12)2 Cl and 3(C12)2 Cl displayed Colh. Guanidinium salts 1(C n )3–4(C n )3 X with three alkoxy chains showed Colh phases. Whereas the use of cyclic guanidinium head groups rather than acyclic ones had only a minor influence on the mesophase properties, melting points were significantly decreased by bent core units instead of linear core units. Replacement of chloride counterions by triflate lead to a further depression of the clearing points and shifted the mesophase towards room temperature.
Acknowledgements
Financial support from the Bundesministerium für Bildung und Forschung (BMBF-Verbundprojekt Nr. 01 RI 05177), the Studienstiftung des Deutschen Volkes (fellowship for M. Butschies), the Deutsche Forschungsgemeinschaft, the Ministerium für Wissenschaft, Forschung und Kunst des Landes Baden-Württemberg, and the Fonds der Chemischen Industrie is gratefully acknowledged. We would particularly like to thank Mr C. Schneck for the important TGA investigations.