Mesomorphic properties of short chains substituted heteroaromatic salts

2014 The synthesis of triaryl-2,4,6 pyrylium tetrafluoroborates substituted by six short (ethyloxy : C2, propyloxy : C3) alcoxy chains has been performed. Classical characterization methods (DSC and optical microscopy) show that these two new compounds present the same columnar phase Dh as that displayed by the other members of the homologous series (C4 to C12). However, these two new compounds are subject to chemical decomposition when heated for a few hours in the mesophase domain of stability but close to Tc. The existence of such a mesophase implies that neighbouring columns be discorrelated. Disordered alcoxy chains are usually assumed to play this role which is however questionable in the case of chains as short as n = 2 or 3. In this case, the BF-4 anions should play a role in the mesophase formation. In order to obtain information about the behaviour of these anions, we have first performed a comprehensive J. Phys. France 51 (1990) 1283-1301 15 JUIN 1990, Classification Physics Abstracts 61.10 61.30 76.60 (*) Associé au CNRS (URA D 0002). (**) UA 429, Chimie et Electrochimie .des Matériaux Moléculaires. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphys:0199000510120128300