Phase behaviour and dynamics of exemplary MHPOBC analogue.

Complementary methods were used to study one of the MHPOBC analogues: 4-(1-methylheptyloxycarbonyl)phenyl-4 ′ nonylbiphenyl-4-carboxylate (MHPNBC). The substance shows rich phase polymorphism. In addition to the para-, ferro- and antiferroelectric phases it exhibits three sub-phases (two ferri- and alpha sub-phase) and a highly ordered room temperature phase. Typical Goldstone mode in the whole temperature range of the SmC * phase and the soft mode in the vicinity of the SmC *– SmA * transition were observed in the dielectric spectra. In the phase two relaxation processes were found: the non-cancellation mode (NCM) and the reorientation around the short molecular axis (S-process). There is only one dielectric relaxation process observed in a highly ordered phase. It is most probably the NCM, whereas the S-process seems to be frozen out. [ABSTRACT FROM AUTHOR]