Water dynamics and interactions in water-polyether binary mixtures.
Water dynamics and interactions in water-polyether binary mixtures.
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DOI：
10.1021/ja809261d
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发表时间：
2009-04-22
影响因子：
15
通讯作者：
Fayer MD
中科院分区：
文献类型：
--
作者：
Fenn EE;Moilanen DE;Levinger NE;Fayer MD
聚氧化乙烯（PEO）是一种重要的高分子材料，在离子交换膜、蛋白质结晶和医疗器械等领域有着广泛的应用。PEO的多功能性源于其与水的特殊相互作用。水分子可以在主链的醚氧之间形成氢键桥。虽然PEO与水的相互作用的稳态测量和理论研究比比皆是，但测量动态观测值的实验却相当稀少。一个主要的问题是水与醚氧的相互作用的性质，而不是高度亲水性的PEO末端羟基。在这里，我们研究了广泛的混合物的水和四甘醇二甲醚（TEGDE），甲基封端的衍生物的PEO与4个重复单元（5醚氧）使用超快红外偏振选择性泵浦探测测量水的羟基伸缩模式，以确定振动弛豫和取向弛豫动力学。由于TEGDE不含PEO末端羟基，因此实验重点关注水与醚主链的动力学相互作用。实验观察到两种不同的水分子亚群：那些与其他沃茨氢键结合的水分子和那些与TEGDE分子结合的水分子。水取向弛豫具有几ps（类水）的快速分量，随后是慢得多的20ps（TEGDE相关）的衰减。这两个衰减时间仅随水浓度轻微变化。这两个亚系综即使在含水量非常低的样品中也是明显的，表明水分子的汇集。随着水含量的降低，无论是通过构象变化的骨干或增加疏水相互作用的结构变化进行了讨论。
Poly(ethylene) oxide (PEO) is a technologically important polymer with a wide range of applications including ion-exchange membranes, protein crystallization, and medical devices. PEO’s versatility arises from its special interactions with water. Water molecules may form hydrogen bond bridges between the ether oxygens of the backbone. While steady-state measurements and theoretical studies of PEO’s interactions with water abound, experiments measuring dynamic observables are quite sparse. A major question is the nature of the interactions of water with the ether oxygens as opposed to the highly hydrophilic PEO terminal hydroxyls. Here, we examine a wide range of mixtures of water and tetraethylene glycol dimethyl ether (TEGDE), a methyl-terminated derivative of PEO with 4 repeat units (5 ether oxygens) using ultrafast infrared polarization selective pump-probe measurements on water’s hydroxyl stretching mode to determine vibrational relaxation and orientational relaxation dynamics. The experiments focus on the dynamical interactions of water with the ether backbone because TEGDE does not have the PEO terminal hydroxyls. The experiments observe two distinct subensembles of water molecules: those that are hydrogen bonded to other waters and those that are associated with TEGDE molecules. The water orientational relaxation has a fast component of a few ps (water-like) followed by much slower decay of ∼20 ps (TEGDE associated). The two decay times vary only mildly with the water concentration. The two subensembles are evident even in very low water content samples, indicating pooling of water molecules. Structural change as water content is lowered either through conformational changes in the backbone or increasing hydrophobic interactions is discussed.
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影响因子：
56.9
作者：
Laage, D;Hynes, JT
通讯作者：
Hynes, JT
DOI：
10.1039/a703436i
发表时间：
1997-11-07
期刊：
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS
影响因子：
--
作者：
Begum, R;Matsuura, H
通讯作者：
Matsuura, H
影响因子：
1.5
作者：
Al-Hamarneh, Ibrahim F.;Pedrow, Patrick D.;Hartenstine, Michael J.
通讯作者：
Hartenstine, Michael J.
影响因子：
3.8
作者：
Crupi, V;Jannelli, MP;Ponterio, R
通讯作者：
Ponterio, R
影响因子：
3.9
作者：
La Rosa, M;Uhlherr, A;Drummond, CJ
通讯作者：
Drummond, CJ