Self-assembled liquid crystals by hydrogen bonding between bipyridyl and alkylbenzoic acids: solvent free synthesis by mechanochemistry

M. MIRANDA; F. VACA CHAVEZ; T. MARIA; M. EUSEBIO; PEDRO J. SEBASTIÃO; M. SILVA

LIQUID CRYSTALS

TAYLOR & FRANCIS LTD

Lugar: Londres; Año: 2014

0267-8292

A series of thermotropic hydrogen-bonded liquid crystalline structures based on 4,4′-bipyridyl and aliphatic carboxylic acids was prepared by a mechanosynthesis technique. This series was characterised by polarising optical microscope, differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction and 1H NMR relaxometry experimental techniques. In these complexes, the bipyridyl component, a non-mesogenic substance by itself, acts as a double H-bond acceptor, whereas the alkylbenzoic acid acts as a Hbond donor, in a 1:2 proportion. The so-formed complexes exhibit mesophases that are not observed by the single components. A characteristic phase (smectic A) is identified and shown to be affected by the alkyl chain length. The isotropisation temperature is increased by the supramolecular aggregation through the H-bonds.