Microsecond time-resolved infrared study of the electric-field-induced reorientation of nematic liquid crystals

Time resolved infrared spectroscopy of electro‐optic switching of 5CB

“…However, our data appear to be fundamentally inconsistent with earlier observations on 5CB and related molecules at much longer time scales, in which such relaxation is found [7,8,13,14]. For example, Urano and Hamaguchi [7] find an apparent delay of about 1 msec in the response of the core relative to that of the tails, which should be quite evident with our setup, but which we do not observe. The origin of such differences is not clear at this time.…”

“…The absence of such effects in our data thus implies its absence in slower experiments, and, indeed, no evidence for internal relaxation is found in several slower experiments [2,20,21]. However, our data appear to be fundamentally inconsistent with earlier observations on 5CB and related molecules at much longer time scales, in which such relaxation is found [7,8,13,14]. For example, Urano and Hamaguchi [7] find an apparent delay of about 1 msec in the response of the core relative to that of the tails, which should be quite evident with our setup, but which we do not observe.…”

“…Some have reported no considerable differences in reorientation rates of the mesogenic core and tails [3][4][5][6]. In other reports, the motion of the flexible tail part precedes that of the core [7,8], and still in others, the motion of the core precedes that of the flexible part [9][10][11][12][13][14].…”

Polarized IR spectra of resonance assisted hydrogen bond (RAHB) in 2-hydroxyazobenzenes

“…As shows already rich literature [1][2][3][4][5][6][7][8][9][10] the polarized IR spectra of liquid crystals (LCs) yield interesting information from the point of view of both the degree of ordering in mesophases and characteristics of particular vibrational modes. Moreover, in the case of liquid crystals there are possibilities to prepare oriented samples, and applying the polarized light, to measure the direction of the transition dipole moment [2].…”

Field-Induced Director Dynamics of Nematic 4-OCTYL-4′-Cyanobiphenyl: A Study By Deuterium NMR Spectroscopy

“…For example, for a nematogen such as 4-pentyl-4 0 -cyanobiphenyl (5CB) vibrational spectroscopy can be used to measure the director orientation via the intensity of peaks associated with the aromatic core or the pentyl chain attached to it. In these techniques [1][2][3][4][5][6][7] an electric field was used to create the non-equilibrium state. Other spectroscopic techniques can also provide molecular site specific information and one of the most important of these for liquid crystals is NMR spectroscopy.…”