Smectic A liquid crystals from dihydrazide derivatives with lateral intermolecular hydrogen bonding

Six dissymmetrical dihydrazide derivatives, N-(4-alkoxybenzoyl)-N′-(4′-nitrobenzoyl) hydrazine (Cn–NO2) and N-(4-alkoxybenzoyl)-N′-(4′-biphenyl carbonyl) hydrazine (Cn–Ph), were synthesized and investigated by means of differential scanning calorimetry, polarized optical microscopy and wide angle X-ray diffraction. The compounds exhibit smectic A1 phase. Based on the results of 1H NMR and variable temperature FT-IR spectroscopy, lateral intermolecular hydrogen bonding between –Cdouble bond; length as m-dashO and –N–H groups was proposed and the effect of hydrogen bonding on the phase transitions was discussed. It was concluded that the combination of lateral intermolecular hydrogen bonding and microphase segregation stabilized the smectic A phase.