Structure and dynamics of chiral ferrielectric phases by deuteron NMR

Abstract

The results of studying angular dependent spectral parameters in a magnetic field are reported in the chiral smectic C phases of a smectogen 1-methylheptyl -(4-n-decyloxybenzoyloxy)-biphenyl-4-carboxylate. Our data provide direct evidence of a phase transition between two ferrielectric phases in this compound, viz. three-layer (SmC*(FiI)) and four-layer (SmC*(FiII)) superlattices. Simulation of spectral patterns of the methyl (C10) deuterons obtained after an aligned sample is rotated by 90 degrees in the magnetic field rules out the "clock model" for the three-layer and four-layer structures in these ferriphases. Instead, our data obtained under a magnetic field (9.4 T) seem to favor an "asymmetric clock model" for the interlayer packing. Interlayer jump rate is also obtained from the simulation of angular dependent spectra in these ferrielectric phases, and compared with those in the antiferroelectric SmC*(A) phase.