Phase transitions in liquid crystal 6O.4 (p-e?‘?-hexyloxybenzylidine-p??-e?‘?-butylaniline)

摘要

DSC measurements on p-e?‘?-hexyloxybenzylidine-p??-e?‘?-butylaniline (6O.4) showed that the crystalline to liquid crystalline (e???a€“e?‘?H) transition at 33.7?°C observed in the heating cycle does not revert even when the sample is cooled down to a?’100?°C. Hence it is inferred that a physically stable supercooled liquid crystalline phase is formed on cooling 6O.4. To investigate the e???a€“e?‘?H transition further the techniques of polarized microscopy and X-ray diffraction were used which concurred with the DSC results. Quasi-elastic neutron scattering measurements carried out to study the re-orientational motions in the ordered phases of 6O.4 (e??? and e?‘?H) show that while in the crystalline phase (at RT) the re-orientational motion is found to involve only the core of the molecule, in the e?‘?H phase (at 45?°C) the dynamics involves the whole molecule and this motion is found to persist even when the sample cools back to room temperature corroborating the results of the DSC, microscopy and X-ray diffraction.