Relaxation Characteristics of Water-ethanol System by Low-field-nuclear Magnetic Resonance
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Abstract:
The 1H LF-NMR and molecular simulation methods were adopted to investigate the water-ethanol solution with different water concentrations. The results indicated that the interaction between hydrogen bond association and water content in water-ethanol solution can cause the relaxation characteristics change. In low concentration of water-ethanol (0%≤XW≤ 10%) system, when adding water to ethanol, part of the water and ethanol tend to form H2O(EtOH)n clusters through hydrogen bonding, multi-component relaxation time T21 at first increases, then decreases and remains relatively constant, while T2W decreased. For the high concentration of water-ethanol (10%≤XW≤100%) system, after minor reduction, T2W increased when the water concentration increased. When 10%≤XW＜30%, due to ethanol self-association and corresponding (H2O)m(EtOH)n clusters, T21 decreases after showing a relatively constant stage. When 30%≤XW≤60%, the saturation of single water molecule combined with ethanol self-association clusters could be reached, T21 turned to be relatively constant. When 60%≤XW≤100%, water self-association would be found and (H2O)m(EtOH)n clusters dissociated, then T21 appeared to increase.
