2H and 13C NMR studies of molecular orientation and dynamics in liquid crystal 6BA

Molecular orientation of hydrogen-bonded liquid crystal (6BA)2-(BPy) x as Studied by 2H NMR

“…For (6BA-d) 2 (BPy) 1 , e 2 qQ/h and ηwere 120 kHz and 0.1, respectively. The e 2 qQ/h and η of the (6BA-d) 2 crystal are 155 kHz and 0.08, respectively [9]. The e 2 qQ/h of 2 H decreases as the strength of the hydrogen bond increases [11].…”

“…In LC I , the orientational fluctuation of molecules increases. The N-I transition temperature of 6BA is 382 K. Around the N-I transition temperature, an open dimer structure of 6BA, where one of two hydrogen bonds is broken, increases and its fluctuation becomes large [8,9]. For (6BA-d) 2 (BPy) 0.5 , the increase in orientational fluctuation of the 6BA dimer with an open dimer structure is predicted to cause a rapid decrease in S.…”

“…In a number of liquid crystals, hydrogen-bonded liquid crystal is particularly attractive, since the creation of a new function is expected by self-assembly through the formation of hydrogen bonds [1][2][3][4][5][6][7][8][9]. For the development of hydrogen-bonded liquid crystal, a detailed analysis of the local structure around a hydrogen bond is very important.…”

“…6BA forms cyclic dimer by two hydrogen bonds between carboxylic acids in the crystal phase (Chart 1(a)). In the nematic phase, an open dimer structure (Chart 1(b)) in which one of two hydrogen bonds is broken, appears and the rate of open dimer increases with increasing temperature [8,9]. When 6BA forms the open dimer structure, it causes a large orientational fluctuation.…”

Nuclear magnetic resonance: a powerful tool to study liquid crystals

“…The analysis of the spectral shape of 2 H NMR spectra of liquid crystals provided an excellent and powerful method to investigate the supramolecular structure of liquid crystals, such as in frustrated phases (TGBA, TGBC* and so on) [24] and ferroelectric (SmC*) phases [25]. Dynamic properties, such as molecular reorientational diffusion, translational self-diffusion and collective motions are mainly investigated by specific NMR approaches, such as NMR diffusometry [26] and NMR relaxometry [27] (which requires specific equipment), or by analysing the spin-spin (T 2 ) and spin-lattice (T 1 ) relaxation times (mainly 1 H and 2 H) through specific models [28][29][30]. In few cases, for instance if molecules are distributed in not homogeneously aligned structures, 2D exchange NMR methods can also be applied [31].…”