Department of Chemistry, Stanford University, Stanford, California 94305, USA.
J Phys Chem B. 2011 Feb 10;115(5):945-50. doi: 10.1021/jp110487j. Epub 2011 Jan 11.
Temperature-dependent rotational diffusion of tetraethylene glycol dimethyl ether (TEGDE) is measured by optical heterodyne-detected optical Kerr effect (OHD-OKE) spectroscopy and compared to previous measurements of rotational diffusion as a function of water content. Both types of data, temperature-dependent and hydration-dependent, follow the Debye-Stokes-Einstein (DSE) equation and agree quantitatively with hydrodynamic calculations. Of particular importance is the result that both types of data show nearly identical dependence on the viscosity divided by the temperature (η/T). We also compare the translational diffusion constants as previously measured by pulsed field gradient spin-echo (PFG-SE) NMR as a function of both temperature and water content. The temperature-dependent data follow the Stokes-Einstein (SE) equation. Similar to the rotation, the low water content mixtures obey the SE equation and show the same proportionality to η/T as the temperature-dependent data. At higher water fractions, the data do not obey the SE equation. The principal results are that the influence of temperature on dry TEGDE orientational relaxation is the same as the influence of water content at fixed temperature, and that the influence of temperature on translational diffusion of dry TEGDE is the same as the influence of water content over a range of relatively low water concentrations. The results demonstrate that there are no large TEGDE structural changes or specific, long-lived water-polyether interactions in the solutions over the entire concentration range.
通过光外差探测光克尔效应（OHD-OKE）光谱测量了四甘醇二甲醚（TEGDE）的温度依赖性旋转扩散，并将其与以前测量的水含量作为函数的旋转扩散进行了比较。这两种类型的数据，即温度依赖性和水合依赖性，都遵循德拜-斯托克斯-爱因斯坦（DSE）方程，并与流体力学计算定量一致。特别重要的是，这两种类型的数据都表现出与粘度除以温度（η/T）几乎相同的依赖性的结果。我们还比较了以前通过脉冲场梯度自旋回波（PFG-SE）NMR 测量的作为温度和水含量函数的平移扩散常数。温度依赖性数据遵循斯托克斯-爱因斯坦（SE）方程。与旋转相似，低水含量混合物遵守 SE 方程，并与温度依赖性数据表现出相同的η/T 比例关系。在较高的水分数下，数据不遵守 SE 方程。主要结果是，在固定温度下，温度对干燥 TEGDE 取向弛豫的影响与水含量的影响相同，而温度对干燥 TEGDE 平移扩散的影响与水含量在相对较低的水浓度范围内的影响相同。结果表明，在整个浓度范围内，溶液中不存在 TEGDE 结构的大变化或特定的、长寿命的水-聚醚相互作用。
