Molecular dynamics above the smectic A-isotropic phase transition of thermotropic liquid crystals studied by NMR

F. VACA CHÁVEZ; R. H. ACOSTA; D. J. PUSIOL

CHEMICAL PHYSICS LETTERS

Año: 2004 vol. 392 p. 403 - 408

0009-2614

This Letter presents a proton fast field cycling Nuclear Magnetic Resonance study of the molecular dynamics in the region abovethe smectic A-isotropic phase transition in thermotropic liquid crystals. The proton spin–lattice relaxation time was measured as afunction of temperature at different Larmor frequencies and the experimental results were interpreted in term of the Landau–DeGennes theory. Mechanisms provided by both individual reorientational fluctuations and fluctuations of the local order parametercan be distinguished at the different Larmor frequency scales.