Lyotropic liquid crystalline main-chain viologen polymers:: Homopolymer of 4,4′-bipyridyl with the ditosylate of trans-1,4-cyclohexanedimethanol and its copolymers with the ditosylate of 1,8-octanediol
Lyotropic liquid crystalline main-chain viologen polymers:: Homopolymer of 4,4′-bipyridyl with the ditosylate of trans-1,4-cyclohexanedimethanol and its copolymers with the ditosylate of 1,8-octanediol
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DOI：
10.1021/ma971115z
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发表时间：
1998-02-10
期刊：
影响因子：
5.5
通讯作者：
Bose, RN
中科院分区：
文献类型：
--
作者：
Bhowmik, PK;Molla, AH;Bose, RN
以4,4′-联吡啶为原料，以反式-1,4-环己二甲醇和1,8-辛二醇为原料，在乙腈中进行季铵化反应，制备了一系列紫胶聚合物。通过粘度测试研究了它们在常见有机溶剂中的多电解质行为，并通过FTIR、1D和2D NMR测定了它们的化学结构。用偏光显微镜和差示扫描量热法对它们在多种极性有机溶剂中的溶致性和紫外-可见光谱对它们的光致变色性质进行了表征。正如预期的那样，在没有添加电解质的情况下，它们在甲醇中的固有粘度随着浓度的增加而急剧下降。虽然这些聚合物都含有沿聚合物链主链的离子基团，但它们中的甲磺酸盐离子和4,4'-联吡啶离子之间存在一组弱离子对偶极子，这可以从其红外光谱中较低频率（1034 cm(-1)）出现S=O的对称拉伸带(与-SO3Na （1064 cm(-1)）相比表明。在每一种聚合物中，4,4'-联吡啶离子的芳香质子都表现出三对信号，这与通常在含有该离子的小分子中出现的一对双偶态相反。这三对信号与离子聚合物在极性溶剂（如甲醇）中的结构和动力学有关，并通过DEFT、H-1-H-1 COSY和NOESY光谱对其进行了研究。它们在甲醇、乙醇、乙二醇、二甘醇、甘油和苯甲醇中均呈溶变层状相。它们的临界浓度（C*值）低至5 wt %，高至20-40 wt %，在各种醇中，它们形成完全成熟的溶嗜相的浓度低至10-20 wt %，高至40-50 wt %，这取决于溶剂的极性、溶剂的亲疏水性和这些聚合物的微观结构。此外，它们的溶性溶液在甘油或苯甲醇中，在紫外线照射下，在没有光敏剂和牺牲供体的情况下，在有空气的情况下产生深蓝色。该深蓝色溶液在390和608 nm处有两条吸收带，这两条吸收带是紫离子阳离子自由基的特征吸收带。这种蓝色的产生是由于4,4'-联吡啶基团通过从甲磺酸反离子的电子转移而光还原而产生的。
A series of viologen polymers based on 4,4'-bipyridyl and the ditosylates of trans-1,4-cyclohexanedimethanol and 1,8-octanediol was prepared by the quaternization reaction in acetonitrile. Their polyelectrolyte behavior in a common organic solvent was studied by viscosity measurements, and their chemical structures were determined by FTIR and 1D and 2D NMR spectroscopies. They were characterized for their lyotropic properties in a number of polar organic solvents by polarizing light microscopy and differential scanning calorimetry and for their photochromic properties by UV-vis spectroscopy. As expected, their inherent viscosity in methanol decreased dramatically with the increase in concentration in the absence of an added electrolyte. Although each of these polymers contained the ionic group along the backbone of the polymer chain, there was an array of weak ion-pair dipoles between the tosylate ion and the 4,4'-bipyridinium ion in each of them, which was indicated by the appearance of symmetric stretching band of S=O at a lower frequency (1034 cm(-1)) when compared with that of -SO3Na (1064 cm(-1)) in its IR spectrum. The aromatic protons of 4,4'-bipyridinium ion in each of these polymers exhibited three pairs of signals as opposed to a pair of doublets that generally occurs in small molecules containing this ion. These three pairs of signals were related to the structure and dynamics of these ionic polymers in a polar solvent such as methanol, which were studied by DEFT, H-1-H-1 COSY, and NOESY spectroscopies. Each of them showed a lyotropic lamellar phase in methanol, ethanol, ethylene glycol, diethylene glycol, glycerine, and benzyl alcohol. Their critical concentrations (C* values) were as low as 5 wt % and as high as 20-40 wt %, and their concentrations for the development of fully grown lyotropic phase were as low as 10-20 wt % and as high as 40-50 wt % in various alcohols depending on the polarity of the solvents, the hydrophilicity and hydrophobicity of the solvents, and the microstructures of these polymers. Additionally, their lyotropic solutions in either glycerine or benzyl alcohol, oh irradiation with UV light, produced a deep blue color in the presence of air, but in absence of both a photosensitizer and a sacrificial donor. This deep blue solution had two absorption bands at 390 and 608 nm, which are the characteristic absorption bands of the viologen cation radical. The generation of this blue color occurred due to the photoreduction of the 4,4'-bipyridinium moiety via the electron transfer from the tosylate counterion.