水-乙醇二元体系的低场核磁共振弛豫特性研究

Relaxation Characteristics of Water-ethanol System by Low-field-nuclear Magnetic Resonance

应用低场核磁共振(1H LF-NMR)技术对不同浓度水-乙醇二元体系的弛豫特性进行了研究,并结合分子模拟计算获得的体系的氢键变化进行了分析。结果表明,不同浓度下水-乙醇体系的氢键缔合状态可引起低场核磁弛豫特性的变化。对0%≤XW≤10%的水-乙醇体系而言,水与乙醇可通过氢键形成H2O(Et OH)n团簇,表现为T21先增加,后减小并保持相对稳定,而单组分弛豫时间(T2w)逐渐减小。对10%≤XW≤100%的水-乙醇体系而言,单组分弛豫时间T2w呈先缓慢减小再逐渐增加的趋势;当10%≤XW<30%时,乙醇分子间缔合为主,形成(H2O)m(Et OH)n团簇,T21先相对稳定再减小。当30%≤XW≤60%时,单体水分子与乙醇自缔合团簇的结合逐渐达到饱和,T21再次呈相对稳定的现象。当60%<XW≤100%时,体系内以水分子间的氢键缔合为主,且(H2O)m(Et OH)n团簇解离,T21呈增大趋势。

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(Et OH)n clusters through hydrogen bonding, multi-component relaxation time T21 at first increases, then decreases and remains relatively constant, while T2 W decreased. For the high concentration of water-ethanol(10%≤XW≤100%) system, after minor reduction, T2 W increased when the water concentration increased. When 10%≤XW<30%, due to ethanol self-association and corresponding(H2O)m(Et OH)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(Et OH)n clusters dissociated, then T21 appeared to increase.