wizyta

od 2020-09-20

Title: Molecular dynamics of n-dodecylammonium chloride in aqueous solutions investigated by 2H NMR and 1H NMR relaxometry

Source: Solid State Nuclear Magnetic Resonance

Year : 2004

Abstract:

Molecular dynamics in n-dodecylammonium chloride/water solutions for concentrations of 34 and 45wt% was studied by 2H NMR and by H-1 NMR dispersion of spin-lattice relaxation in the 2 kHz-90 MHz frequency range. The system exhibits a number of lyotropic liquid crystalline phases, which differ in symmetry and involve motions characterized by a wide frequency scale. The analysis of H-2 NMR lineshapes of selectively deuterated DDACl molecules gave us an evidence for local trans-gauche conformational changes in the chains, whereas the dispersion of spin-lattice relaxation times T, explored by fast field cycling method revealed fast local motions, translational diffusion and collective molecular dynamics of the chains. In particular, we have found that the order director fluctuation mechanism in smectic and nematic phases dominates spin-lattice relaxation below I MHz and that local motions and translational diffusion are responsible for the spin-lattice relaxation in the higher Larmor frequency range.
(C) 2003 Elsevier Inc. All rights reserved.

DOI: 10.1016/j.ssnmr.2003.07.002   (Pobrane:  2020-10-21)