Conformational properties of short poly(oxyethylene) chains in water studied by IR spectroscopy
Conformational properties of short poly(oxyethylene) chains in water studied by IR spectroscopy
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DOI：
10.1039/a703436i
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发表时间：
1997-11-07
期刊：
影响因子：
--
通讯作者：
Matsuura, H
中科院分区：
文献类型：
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作者：
Begum, R;Matsuura, H
用红外光谱法研究了短链聚氧乙烯（POE）化合物在水中的构象性质。所研究的化合物为CH_3（OCH_2CH_2）（m）OCH_3（m = 1-4），CH_3CH_2（OCH_2CH_2）（2）OCH_2CH_3，CH_3（OCH_2CH_2）（m）OH（m = 2-4），CH_3CH_2（OCH_2CH_2）（m）OH（m = 2和3）、CH 3（CH 2）（3）（OCH 2CH 2）（m）OH（m = 2和3）、H（OCH 2CH 2）（m）OH（m = 1-4和6）、PEG 600和PEG 2000。在不同的溶液浓度下测量了C-C键和C-O键的交叉和反式构象关键带的相对强度，并研究了链长和端基对各自键周围构象的影响。C-C键周围的gauche构象的相对群体随着水分数的增加而显着增加。在实践中，只要其是丁基或更短的基团，则笨拙群体的增加速率不取决于POE链的长度和末端烷基的长度。末端羟基的存在大大抑制了水溶液中C-C键周围的偏折构象。C-O键的构象随溶液浓度的变化远小于C-C键的构象随溶液浓度的变化。对于具有烷基末端的化合物，C-O键周围的反式构象的群体仅随着水分数的增加而略微增加，但对于具有羟基末端的化合物，没有观察到实质性的构象变化。C-C键的构象行为表明POE链和水之间存在几种类型的氢键。一种是通过相邻醚氧原子之间的水分子形成的氢键桥，另一种是通过被两个氧杂环单元隔开的醚氧原子之间的一个或多个水分子形成的桥。末端O-CH 2-CH 2-OH链段的受约束的笨拙偏好可以由不稳定的水合作用来解释。链的末端部分周围的结构。本研究结果表明，在POE链在水中的构象稳定中，POE链和水之间的氢键和结构匹配的重要性。
Conformational properties of short-chain poly(oxyethylene) (POE) compounds in water have been studied by IR spectroscopy. The compounds examined are CH3(OCH2CH2)(m)OCH3 (m = 1-4), CH3CH2(OCH2CH2)(2)OCH2CH3, CH3(OCH2CH2)(m)OH (m = 2-4), CH3CH2(OCH2CH2)(m)OH (m = 2 and 3), CH3(CH2)(3)(OCH2CH2)(m)OH (m = 2 and 3), H(OCH2CH2)(m)OH (m = 1-4 and 6), PEG 600 and PEG 2000. The relative intensities of the gauche and trans conformational key bands of the C-C and C-O bonds have been measured with varying solution concentration, and the effects of the chain length and the terminal group on the conformation around the respective bonds have been studied. The relative population of the gauche conformation around the C-C bond increases significantly with increasing water fraction. The rate of increase in the gauche population does not depend practically on the length of the POE chain and the length of the terminal alkyl group as long as it is a butyl or shorter group. The terminal hydroxy group greatly restrains the preference of the gauche conformation around the C-C bond in water. The conformational change of the C-O bond with varying solution concentration is much smaller than that of the C-C bond. The population of the trans conformation around the C-O bond increases only slightly with increasing water fraction for the compounds with alkyl terminals, but no substantial conformational changes are observed for the compounds with hydroxy terminal(s). The conformational behaviour of the C-C bond suggests the presence of several types of hydrogen bonds between the POE chain and water. One is a hydrogen-bonded bridge by a water molecule between the adjacent ether oxygen atoms, and the others are bridges by one or more water molecules between the ether oxygen atoms separated by two oxyethylene units. The restrained gauche preference of the terminal O-CH2-CH2-OH segment may be accounted for by the destabilised hydration. structure around the terminal part of the chain. The present results have shown the importance of both the hydrogen bonding and the structural matching between the POE chain and the water in the conformational stabilisation of the POE chain in water.