Dynamics and Orientation Ordering of Water in Lyotropic Liquid Crystals Using 2H Double Quantum Filtered NMR Spectral Analysis

Abstract

AbstractThe alignment of lyotropic liquid crystals in a magnetic field has been studied by line shape analysis of the T1 process and 2D 2H double quantum filtered (DQF) NMR to investigate water dynamics and orientational feature in Cetyltrimethylammonium bromide (CTAB)/Sodium Salicylate (NaSal)/D2O liquid crystals. The same system but in powder form was also examined. In the ordered liquid‐crystalline phase, the single quantum line shapes showed splitting of doublets due to the residual quadrupolar interaction, while the double quantum spectra observed splitting patterns with damped oscillation. The modified cone model is invoked to describe the restricted motions of bound D2O molecules. Ten to thirteen bound water molecules are found to associate with each CTAB molecule and the correlation time of wobbling motion of the bound water is in the time scale of 10−8 s. At 10°C, the motional correlation times of water in the powder sample have the same magnitude as those in the oriented sample. This study shows that the analysis of DQF relaxation spectra provides a more detailed source of motional information than the normally used measurements.