Influence of cooling rate on the phase transitions of ferroelectric liquidcrystals, MBOPDOB and MBOPDoOB

The phase transitions of ferroelectric liquid crystals (FLCs), D-4-(2-methy lbutyloxy) phenyl 4-decyloxybenzoate (MBOPDOB) and D-4-(2-methylbutyloxy)ph enyl 4-dodecyloxybenzoate (MBOPDoOB), were investigated by means of differe ntial scanning calorimetry (DSC) and polarizing microscopy. The DSC and pol arizing microscopy results show that MBOPDOB and MBOPDoOB exhibit different phase transition sequences on slow cooling, whereas they have the same seq uence under rapid cooling. In MBOPDoOB, we also observed a quench-induced m etastable phase that differs from the normal crystal phase formed by slow c ooling. The textures corresponding to the two crystal phases were observed using a polarizing microscope. X-ray diffraction (XRD) was also used to stu dy the quench-induced phase. The influence of the alkoxy chain length on th e molecular interactions in FLCs is discussed.