HYDROGEN-BONDED LIQUID-CRYSTALS FROM NITROPHENOLS AND ALKOXYSTILBAZOLES

Three series of hydrogen bonded adducts have been formed between 4-alk oxy-4'-stilbazoles dagger and the nitrophenols 4-nitrophenol, 3-nitrop henol and 2,4-dinitrophenol. Each series is mesomorphic displaying bot h nematic and smectic A phases, in sharp contrast to the behaviour of the individual components. The binary phase behaviour of mixtures of 3 -nitrophenol and 4-octyloxystilbazole is reported, and gives conclusiv e evidence for the formation of a one-to-one hydrogen bonded adduct. E lectronic spectroscopy of 2,4-dinitrophenol/decyloxystilbazole was ver y informative and showed that the higher energy, ionic hydrogen bonded state, corresponding to proton transfer, was significantly populated through the mesophase, and that the mesophase provides an additional s tabilisation for this state.