Matin Md Ruhul, Katsumoto Yukiteru, Matsuura Hiroatsu, Ohno Keiichi
Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
J Phys Chem B. 2005 Oct 27;109(42):19704-10. doi: 10.1021/jp0527554.
Hydration of short-chain poly(oxyethylene)s, CH(3)(OCH(2)CH(2))(m)OCH(3) (abbreviated as C(1)E(m)()C(1)) (m = 1-3), in carbon tetrachloride has been studied by infrared spectroscopy. The O-H stretching vibrations of water in ternary solutions with H(2)O:C(1)E(m)C(1):CCl(4) mole ratios of 0.000418:0.005:0.995 to 0.000403:0.04:0.96 were analyzed. Two types of hydrogen bonds are formed in the interaction between water and C(1)E(m)C(1) in carbon tetrachloride; one is a monodentate hydrogen bond, in which only one of the O-H bonds of a water molecule participates in hydrogen bonding, and the other is a bidentate hydrogen bond, in which both of the O-H bonds of a water molecule participate in hydrogen bonding by bridging oxygen atoms separated by two or more monomer units on the polymer chain. An important finding is that the bidentate hydrogen-bond bridge is not formed between the nearest-neighbor oxygen atoms. This experimental observation supports the results of previous molecular dynamics simulations. The shortest oligomer of poly(oxyethylene), i.e., CH(3)OCH(2)CH(2)OCH(3) (1,2-dimethoxyethane) with a single monomer unit, is suggested not to be an adequate model for this polymer with respect to hydrogen bonding to water. The hydrogen bonding in a 1:1 C(1)E(m)C(1)-water adduct in carbon tetrachloride represents primitive incipient hydration of poly(oxyethylene). The present results indicate that both monodentate and bidentate hydrogen bonds are important and the latter is destabilized more rapidly than the former with increasing temperature. This dehydration process can be a potential mechanism of the poly(oxyethylene)-water phase separation.
通过红外光谱研究了短链聚氧乙烯CH(3)(OCH(2)CH(2))(m)OCH(3)（简称为C(1)E(m)C(1)，m = 1 - 3）在四氯化碳中的水合作用。分析了H(2)O:C(1)E(m)C(1):CCl(4)摩尔比为0.000418:0.005:0.995至0.000403:0.04:0.96的三元溶液中水的O - H伸缩振动。在四氯化碳中，水与C(1)E(m)C(1)相互作用时形成了两种类型的氢键；一种是单齿氢键，其中水分子的仅一个O - H键参与氢键形成，另一种是双齿氢键，其中水分子的两个O - H键通过聚合物链上相隔两个或更多个单体单元的桥连氧原子参与氢键形成。一个重要发现是双齿氢键桥不是在最近邻的氧原子之间形成的。这一实验观察结果支持了先前分子动力学模拟的结果。聚氧乙烯的最短低聚物，即具有单个单体单元的CH(3)OCH(2)CH(2)OCH(3)（1,2 - 二甲氧基乙烷），就与水形成氢键而言，被认为不是该聚合物的合适模型。在四氯化碳中1:1的C(1)E(m)C(1) - 水加合物中的氢键代表了聚氧乙烯的原始初始水合作用。目前的结果表明，单齿和双齿氢键都很重要，并且随着温度升高，后者比前者更快地失稳。这种脱水过程可能是聚氧乙烯 - 水相分离的潜在机制。
