Phase transition behavior of hydrogen bonded liquid crystal (6BA) 2 -(BPy) x as studied by 2 H NMR

The thermal properties and the orientational order of hydrogen-bonded liquid crystals (6BA) 2 -(BPy) 0.4 and (6BA) 2 -(BPy) 0.3 (6BA: 4- n -hexylbenzoicacid, BPy: 4,4’-bipyridine) were investigated by DSC and 2 H NMR. On cooling, isotropic liquid - liquid crystal phase transition temperatures were T C = 409 and 405 K for (6BA) 2 -(BPy) 0.4 and (6BA) 2 -(BPy) 0.3 , respectively. Thermal anomalies in the liquid crystal phase were observed at T LC1 = 402 and T LC2 = 375 K for (6BA) 2 -(BPy) 0.4 and at T LC1 = 398 and T LC2 = 375 K for (6BA) 2 -(BPy) 0.3 . For (6BA) 2 -(BPy) 0.4 , only the smectic component was created above T LC1 . In addition, the nematic component was created below T LC1 . The nematic component gradually changed to the smectic component with decreasing temperature and only the smectic component was observed below T LC2 . For (6BA) 2 -(BPy) 0.3 , only the nematic component was created above T LC2 . The phase transition from the nematic phase to the smectic phase took place at around T LC2 .