title: Dynamics of the Chiral Liquid Crystal 4'-Butyl-4-(S)-(2-methylbutoxy)azoxybenzene in the Isotropic, Cholesteric, and Solid Phases: A Fast Field-Cycling NMR Relaxometry Study.
abstract: (1)H NMR relaxometry was applied to investigate dynamic processes in the isotropic liquid, cholesteric, and crystalline phases of the chiral mesogen 4'-butyl-4-(S)-(2-methylbutoxy)azoxybenzene (4ABO5*). To this aim, (1)H longitudinal relaxation rates were measured as a function of temperature (between 257 and 319 K) and Larmor frequency (from 10 kHz to 35 MHz by a fast field-cycling relaxometer and at 400 MHz by an NMR spectrometer). The NMR relaxation dispersion (NMRD) curves so obtained were analyzed in terms of models suitable for the description of dynamic processes in the different phases, thus quantitatively determining values of characteristic motional parameters. In particular, internal and overall rotations/reorientations, molecular translational diffusion, and collective motions contribute to relaxation in the isotropic and cholesteric phases, whereas, in the crystalline phase, relaxation is mainly determined by internal motions and molecular reorientations. The results were discussed and compared with those previously obtained on the same compound by dielectric relaxation spectroscopy.
authors.affiliation: Consiglio Nazionale delle Ricerche - CNR, Istituto di Chimica dei Composti OrganoMetallici, via G. Moruzzi 1, 56124 Pisa, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Carignani
authors.affiliation: Consiglio Nazionale delle Ricerche - CNR, Istituto di Chimica dei Composti OrganoMetallici, via G. Moruzzi 1, 56124 Pisa, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Calucci
authors.affiliation: The Henryk Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences , E. Radzikowskiego 152, 31-342 Krakow, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Juszyńska-Gałązka
authors.affiliation: The Henryk Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences , E. Radzikowskiego 152, 31-342 Krakow, Poland.
authors.forename: Mirosław
authors.initials: M
authors.lastname: Gałązka
authors.affiliation: The Henryk Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences , E. Radzikowskiego 152, 31-342 Krakow, Poland.
authors.forename: Maria
authors.initials: M
authors.lastname: Massalska-Arodź
authors.affiliation: Consiglio Nazionale delle Ricerche - CNR, Istituto di Chimica dei Composti OrganoMetallici, via G. Moruzzi 1, 56124 Pisa, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Forte
authors.affiliation: Consiglio Nazionale delle Ricerche - CNR, Istituto di Chimica dei Composti OrganoMetallici, via G. Moruzzi 1, 56124 Pisa, Italy.|Dipartimento di Chimica e Chimica Industriale, Università di Pisa , via G. Moruzzi 13, 56124 Pisa, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Geppi