NMR study of diffusive processes in novel liquid crystalline phases

作者：Dong Ronald Y^*

来源：Thin Solid Films, 2008, 517(4): 1367-1379.

DOI：10.1016/j.tsf.2008.09.043

• Rotation diffusion
• Jump diffusion
• Spectral simulation
• Spectral density
• Phase structure
• Chiral phases
• Discotic phase
• Spin relaxation

Various deuterium one- and two-dimensional (2D) NMR techniques are used in the present study to characterize molecular self-diffusive processes in some novel mesophases. Both aligned and powder samples of liquid crystals (LC) are chosen to investigate rotational and/or translational jump diffusions It is demon. strated that rotation of aligned LC samples in a NMR goniometer probe can be helpful in obtaining dynamic and structural information. Both spectral simulations and/or pulse separation (tau) dependences of the quadrupole echo intensity are successfully employed. Deuteron spin-lattice relaxation times and angle dependent spectra are measured in a columnar phase of a monomeric discotogen to illustrate both the fast and intermediate motion regimes. jump diffusions of chiral rodlike molecules in various smectic C* (SmC*) phases and twist grain boundary A* (TGBA*) phase are studied. In the LC 10131M7, the jump rate (or diffusion constant) is determined as a function of temperature in the ferro-, ferri- and antiferro-electric chiral C* phases. 2D deuterium exchange NMR is used to monitor the dynamic processes (self-diffusion) in the ferroelectric SmC* and TGBA* phases. Moreover, packing information of the phase can also be obtained in the two ferrielectric subphases and TGBA* phase, which can be compared With results obtained by X-rays measurements.

• 出版日期2008-12-31