Deuterium NMR investigations of field-induced director alignment in nematic liquid crystals

The twist-bend nematic phase: translational self-diffusion and biaxiality studied by 1H nuclear magnetic resonance diffusometry

“…This is reminiscent of the alignment process for the director of a nematic with a positive anisotropic susceptibility when the aligning field is initially perpendicular to it. [36] The alignment progresses in the N TB for some considerable time as is apparent from the stack plot shown in Figure A2. Figure A2.…”

“…Following the sample rotation the NMR spectra can be measured in a continuous time-resolved NMR experiment. [36 ] The measurement of the 2 H NMR spectra of CB7CB-d 4 was made in a Varian Infinity Plus 300 spectrometer using a quadrupolar echo sequence ( 2 H Larmor frequency 46 MHz). The 90º pulse was of 5µs duration and the spectra were acquired using a spectral width of 150 kHz saved in a 4K memory file.…”

“…The spectra also contain information about the field-induced alignment process; [36] thus it is apparent from the spectral intensity between the two perpendicular lines that that some of the helix axis is starting to be aligned by the magnetic torque at angles less than 90°. The significant width of these peaks shows that the helix axis is widely distributed as it rotates towards being parallel to the magnetic field.…”

“…This again demonstrates that the helix axis is not aligned as a monodomain. [36] Indeed this is apparent from the variation in the spectral intensities and not simply from the location of the peaks. It is difficult to make a quantitative comparison with how the field-induced helix dynamics change with temperature and indeed with other dynamic processes.…”

Nuclear magnetic resonance: a powerful tool to study liquid crystals

“…Figure 2 (a)). Recent advancements in the field of liquid crystals, such as the understanding of the director reorientational behaviour in nematic phases in presence of the electric field [9], the explanation of the supramolecular structure of the twisted nematic phase [10] [16]. Papers focused on these nuclei represent more than 33% of total papers published in the last 50 years (see Figure 2(a)).…”