Phase transitions and conformational changes in an antiferroelectric liquid crystal 4-(1-methylheptyloxycarbonyl)phenyl 4′-octyloxybiphenyl-4-carboxylate (MHPOBC)

Renewed focus on the small temperature change of smectic layer spacing in ferroelectric and antiferroelectric LCs

“…The previously reported smectic layer spacing determined by X-ray diffraction is also given for comparison. [11,40,41] Both temperature variations are surprisingly similar. We would obtain S app ¼ 1 when all molecules align along the smectic layer normal.…”

“…Actual modulation must be much more irregular and disordered, and the actual size, shape and ordering of concentric regions are interesting problems to be solved in the future, as pointed out by Sirota. [17] Using sophisticated IR spectroscopic technique, Korlacki et al [18] showed that the 'antiferroelectric' phase that has so far been identified as 'anticlinic HxI Ã A ' [11,40,41] should be better identified as 'modulated HxB' and that the electric-field-induced phase transition from this phase to ferroelectric synclinic HxI Ã can be considered as the giant electroclinic effect due to the opening of closed modulation loops. They prepared homeotropically aligned cells in SmA with the tilting directions in SmC Ã /SmC Ã A sufficiently random within the IR beam.…”

The Structure and Properties of Antiferroelectric Liquid Crystals

“…The investigation of the switching mechanism under application of electric f eld by time-resolved FTIR spectroscopy [48] shows that all the molecular segments reorient simultaneously, at least in the microsecond Iange. These methods do not provide direct information about the structure of ferrielectric phases; however, a careful analysis of the experimental results enables a validation of the structure of some phases, such as SmCi and even SmC; [47]. In addition to the various experimental techniques mentioned above, several analytical methods have been widely used for studying AFLCs.…”

“…Careful analysis of the relative intensity of scattering peaks based on the structure factor calculations shows that the angle between the tilt directions in any pair of neighboring smectic layers is Acp = 27t/n, where n is number of sniectic layers in a periodic unit [46]. This is consistent with the structures, suggested by the clock models [28-301. Recently Raman light scattering [47] and Fourier transform infrared (FTIR) spectroscopy [48-5 11 have been err ployed for investigating the molecular conformation and the hindered rotation of different molecular groups in AFLC. The results of FTIR spectroscopy shows that the rotation of both chiral and core carbonyl C=O groups aroind the long molecular axis is hindered in tilted smectic phases [48-5 11.…”

Liquid Crystal Droplets Dispersed in Ferroelectric Copolymer of Vinylidene Fluoride and Trifluoroethylene

“…Spontaneous polarization Jump A is the transition from Crystal III to phase of MHPOBC. 12 Peak B corresponds to successive transitions from Sm-C Sm-A phase, 16 and peak C ferroelectric-paraelectric transition ofP(VDF/TrFE). P 8 of the crystal of MHPOBC might be comparable to 1 mCm -2 the typical Ps ofMHPOBC in the liquid crystal phase.…”