title: Molecular dynamics in the smectic a and C phases in a long-chain ferroelectric liquid crystal: 2H NMR, dielectric properties, and a theoretical treatment.
abstract: In this work, the rotational-diffusion coefficients D(parallel) and D(perpendicular) for the ferroelectric smectogen (+)-(S)-4-[4'-(1-methylheptyloxy)] biphenyl 4-(10-undecenyloxy)benzoate have been studied by means of 2H NMR spectroscopy in the smectic C phase, using a new theoretical approach (Domenici,V.; Geppi, M.; Veracini, C. A. Chem. Phys. Lett. 2003, 382, 518). The analysis of spin-lattice relaxation times has been performed in terms of the diffusional constant and the activation energy of the internal and overall molecular-reorientational motions, and the results are compared to the smectic A (SmA) phase. Moreover, from the 2H NMR data in the SmA phase, the dielectric permittivity and the dielectric relaxation time functions are investigated using a theoretical approach. The longitudinal and transverse components of the real Rchigammaomega and imaginary chigammaomega (gamma = parallel, perpendicular) parts of the complex susceptibility tensor and the nematic-like rotational-viscosity coefficients, lambda2 and lambda5, are calculated.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università degli studi di Pisa, via Risorgimento 35, 56126, Italy. valentin@dcci.unipi.it
authors.forename: Valentina
authors.initials: V
authors.lastname: Domenici
authors.forename: Marco
authors.initials: M
authors.lastname: Geppi
authors.forename: Carlo Alberto
authors.initials: CA
authors.lastname: Veracini
authors.forename: Alexandre V
authors.initials: AV
authors.lastname: Zakharov