Synthesis and mesomorphic behaviour of hexacatenar di-hydrazine derivatives

Abstract

A new series of hydrazide derivatives of N,N-bis(3,4,5-tris(heptyloxy)benzoyl) (T7 series) were designed and synthesised. Investigations on the liquid crystalline properties by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarising optical microscopy (POM) showed that the di-hydrazine derivatives exhibited different mesophases, which were ascribed to the different structure of T7 series. The rectangular columnar mesophases of T7-ben remained stable down to room temperature during cooling, T7-fuma was decomposed at 259°C in the first heating, while T7-mal showed simple cubic mesophase and crystalline phase at room temperature during cooling. Comparing Fourier-transformed infrared (FTIR) at room temperature of T7 series, some differences were found in the N–H stretching vibration and C = O stretching vibration bands, indicating that T7 series had some differences in intermolecular hydrogen bond strength, which were caused by the different linking unit of T7 series. Intermolecular hydrogen bonding between –C = O and –N–H groups in crystalline and liquid crystalline phases was confirmed by temperature FTIR spectroscopy and temperature 1H NMR spectroscopy.