Advances in Proton NMR Relaxometry in Thermotropic Liquid Crystals

Study of Liquid Crystals Showing Two Isotropic Phases by 1H NMR Diffusometry and 1H NMR Relaxometry

“…2 H NMR spin-lattice relaxation times, T 1 , typically measured at high Larmor frequencies (hundreds of MHz), are sensitive to fast motions, such as overall molecular motions having 10 −11 < τ c < 10 −7 s, while 2 H NMR spin-spin relaxation times, T 2 , can be used to investigate collective and other slow motions, with τ c ranging from 10 −6 s up to 10s [31,[40][41][42]49,50]. Another important NMR technique is represented by 1 H NMR relaxometry, based on the experimental measurement of 1 H spin-lattice relaxation times, T 1 , at different 1 H Larmor frequencies, typically from few KHz to several tens of MHz [49][50][51][52]. The analyses of the frequency-dependence of 1 H NMR T 1 can be done invoking different dynamic contributions by means of suitable theoretical models [51][52][53][54][55][56][57][58][59].…”

1H NMR Relaxation Study of a Magnetic Ionic Liquid as a Potential Contrast Agent

“…12 The effect of paramagnetic relaxation can be described by the so-called Curie relaxation that considers fluctuations of the dipolar interactions between the paramagnetic particles 3 global magnetic moments and the proton nuclear magnetic moments of neighbor hydrogen nuclei either temporary bounded to the magnetic particle or within the first neighbor layer spheres (inner-spheres) or in outer layer spheres. 6,[13][14][15][16] Nowadays, the commercial contrast agents are based on Gd (III) paramagnetic ion, due to high magnetic response in comparison with the others metal ions described before. 12 However, the toxicity of these compounds as contrast agents are high.…”

Recent NMR Studies of Thermotropic Liquid Crystals

“…For all mesophases, model fit of the experimental T À1 1 ðω, TÞ results in 10BBL were performed using a global target leastsquare minimization. It was found that the T 1 dispersion curve above 50 MHz was dominated by ROT as observed in most N, TGB*, SmA, SmC, and SmC* phases of other LCs [171]. The T 1 results presented in the BP have led the authors to conclude that the specific diffusion/rotation (RMTD) process along the helical axes of BP was very important (also in the TGB* phases) in10BBL at Larmor frequencies below $50 kHz.…”