1.1H NMR Relaxometric Study of Molecular Dynamics in a "de Vries" Liquid Crystal.
Gradišek A, Domenici V, Apih T, Novotna V, Sebastião PJ. J Phys Chem B. 2016 May 2. [Epub ahead of print]
Liquid crystals that exhibit de Vries smectic A phases are promising materials for new generations of ferroelectric liquid crystal displays and other electro-optical devices. We investigated the molecular dynamic properties of a rod-like de Vries liquid crystal compound, namely the 9HL, a (S)-hexyl-lactate derivative, in the whole mesophasic range. This is the first molecular dynamic investigation on a de Vries phase, and the interest of this system is related to the understanding of the structural and supramolecular organization of de Vries SmA phases, which has been a subject of a broad scientific debate in the last years. Proton NMR spin-lattice relaxation times, T1, were measured in the range 100 MHz - 5 kHz, thus covering a very wide range of motional regimes. 1H NMR dispersion curves and temperature-dependent relaxation rates were analyzed with a global minimum target fitting approach and the main molecular motions, namely reorientational diffusion, translational self-diffusion, layer undulation, and tilting director fluctuations were fully characterized.