【作者】 谭磊；

【导师】 杨亚江；

【作者基本信息】 华中科技大学 ， 高分子化学与物理， 2009， 博士

【摘要】 小分子量化合物凝胶因子可通过分子间氢键、π-π相互作用，以及其它非共价键作用形成超分子聚集体结构进而形成稳定的超分子凝胶。由于其具有介于固、液体之间的特性，被广泛应用在催化、电解质材料等领域。离子液体是由阴离子和阳离子组成的离子化合物，由于其液相温度范围宽、不挥发、高沸点、溶解性好、电导率高且电化学稳定窗口宽等优良性能日益受到广泛关注，尤其是在高效的电解质材料领域具有极大的应用前景。本文通过分子设计的方法将酰胺基团、苯环和烷基链引入凝胶因子的分子结构中，合成出三类结构不同的凝胶因子(4，4′-二（n-烷基酰胺基）二苯醚（简称BSDE-n，n为烷基链长，下同）；4，4′-二（n-烷基酰胺基）二苯甲烷（简称BSDM-n）；2，4-二（n-烷基酰胺基）甲苯（简称BSUT-n）。研究了三类凝胶因子在有机溶剂中凝胶化性能及自组装机理。侧重研究了三类凝胶因子在不同离子液体中的凝胶化，制备了离子液体超分子凝胶。研究了离子液体超分子凝胶的电化学性能和流变学性质。本论文包括以下主要内容：1、通过分子设计的方法合成的凝胶因子（BSDM-n，BSDE-n，BSUT-n）能在20多种有机溶剂中发生聚集、自组装，进而在这些有机溶剂中形成热可逆的超分子凝胶。分别研究了凝胶因子结构、凝胶因子浓度以及不同溶剂体系对凝胶体系的相转变温度(T_GS)和最低凝胶化浓度（MGC）的影响。2、在三类凝胶因子的作用下，制备了离子液体[bmim]PF₆超分子凝胶。凝胶化性能最好的三种凝胶因子分别为4，4′-二（辛酰胺基）二苯醚（简称BSDE-8），4，4′-二（辛酰胺基）二苯甲烷（简称BSDM-8），2，4-二（辛酰胺基）甲苯（简称BSUT-8）。结果表明，凝胶因子的最低凝胶化浓度按BSDE-8，BSDM-8，BSUT-8的顺序增加。离子液体超分子凝胶相转变温度T_GS按BSDE-8，BSDM-8，BSUT-8的顺序减小。采用偏光显微镜研究了凝胶因子在离子液体中的自组装机理，结果表明，凝胶因子首先形成纤维状聚集体并进一步聚集形成球晶状结构。3、采用线性电位扫描，循环伏安法和交流阻抗法等电化学测试方法，研究了离子液体超分子凝胶的电化学性能。结果表明，凝胶体系具有较宽的电化学稳定窗口，一般为—2．6V到2．6V。采用BSDE-8制备的离子液体凝胶的电化学窗口为—2．6V到1．6V，这主要是由于BSDE-8分子中醚氧键（—O—）在1．6V处容易被氧化。电导率随温度的变化关系符合阿累尼乌斯方程，且凝胶体系电导率同纯离子液体电导率差别在同一数量级。BSDE-8离子液体超分子凝胶的电导率最高，是因为醚氧键（—O—）与苯环之间的大π键容易导致凝胶因子之间的π-π堆积，增强了凝胶因子之间的作用力，减少了凝胶体系中凝胶因子与离子液体之间的相互作用，使得更多的离子能够参与导电。因此，凝胶因子的结构对离子液体超分子凝胶体系的电化学行为有重要影响。4、用ARES流变仪研究了三种离子液体超分子凝胶体系的流变学性质。应变扫描结果表明，当应变振幅为0．4％时，三种离子液体超分子凝胶体系的应变在其线性粘弹区内。频率扫描结果表明，随着剪切速率的增加，凝胶体系的弹性模量（G′）和粘性模量（G″）随之增加，高浓度体系的弹性模量（G′）和粘性模量（G″）分别比低浓度体系的高。凝胶体系的tanδ在整个频率范围内均小于1，凝胶因子浓度较低时，tanδ随频率的增加而减小；浓度较高时tanδ随频率的增加先减小后增大。凝胶体系复合粘度η^*随着凝胶因子浓度的增加在同一剪切频率下也增加，而在同一凝胶因子浓度下凝胶体系复合粘度η^*随剪切频率的增加而减小，呈现剪切变稀性质。温度扫描结果表明，随着温度的增加，离子液体凝胶体系的弹性模量（G′）和粘性模量（G″）均增大，在整个温度范围内G′＞G″，凝胶体系表现固态弹性行为。凝胶体系tanδ随温度的增加先升高后减小，在测试范围内tanδ＜1。凝胶体系的复合粘度η^*随温度的升高而增加。在相同温度、相同剪切速率及相同凝胶因子浓度的条件下，离子液体超分子凝胶体系的弹性模量G′和复合粘度η^*均按BSDE-8，BSDM-8，BSUT-8的顺序减小。这是因为三种凝胶因子相比，BSDE-8分子间最容易形成π-π堆积，增强了凝胶因子之间的作用力，使形成的凝胶因子聚集体三维网络结构更致密，导致凝胶体系具有更高的复合粘度η^*和弹性模量G′。因此，凝胶因子的结构对离子液体超分子凝胶体系的流变学行为有重要影响。更多还原

【Abstract】 In recent years, supramolecular gels formed by the self-assembly of gelators throughintermolecular hydrogen bonding,π-πstacking and other non-covalent bond interationswere applied on catalyzer, electrolyte and other fields because of its properties between theliquids and solids. Ionic liquids composed of anions and cations have useful properties suchas extremely low volatility, high thermal stability, wide liquid phase temperature range,nonflammab- ility, high chemical stability, high ionic conductivity, and a wideelectrochemical window. These advantages implied that ionic liquids would play animportant role in such technological applications as electrolyte materials.Three kinds of gelators named 4,4’-bis（N’-octanamino）diphenyl ether （BSDE-n）、4,4’-bis （N’-octanamino）diphenyl methane （BSDM-n） and 2,4’-bis（N’-octanureido）toluene（BSUT-n） were synthesized by using functional groups such as amide group, benzenegroup and alkyl chains in molecular designing way. The gelation abilities of supramoleculargels could be obtained by controlling the length of alkyl chains, and then the mechanism ofself-assembly and gelation abilities in organic solvents were investigated. Gelators weretried to gel ionic liquids, and then ionic liquids supramolecular gels were formed. Threekinds of gelators named 4,4’-bis（octanamino）diphenyl ether （BSDE-8）. 4,4’-bis（octanamino）diphenyl methane （BSDM-8） and 2,4’-bis（octanureido）toluene （BSUT-8） andthe ionic liquid [bmim]PF₆ were chosen as they formed the better ionic liquidsupramolecular gels. The electrochemical properties and rheological behavior of gels wereinvestigated by using those ionic liquids supramolecular gels.This paper is consisted of several sections as the following:1. Three kinds of gelators named 4,4’-bis（N’-octanamino）diphenyl ether （BSDE-n）、4,4’-bis （N’-octanamino）diphenyl methane （BSDM-n） and 2,4’-bis（N’-octanureido）toluene（BSUT-n） which were synthesized by using functional groups such as amide group、benzene group and alkyl chains by molecular designing could be self-assemblied in morethan 20 kinds of organic solvents.The influrence of gelator types, different gelatorconcentrations, different solvents to gel-sol phase dissociation temperature(T_GS) and minimum gelation concentrations were discussed. The morphology and structures ofsupramolecular gels in organic solvents were characterized by POM and FE-SEM.2. Ionic iquids supramolecular gels were formed by using three kinds of gelators and theionic liquid [bmim]PF₆. The gelation abilities of ionic iquids supramolecular gels werediscussed. Three kinds of gelators named 4,4’-bis（octanamino）diphenyl ether （BSDE-8）、4,4’-bis（octanamino）diphenyl methane （BSDM-8） and 2,4’-bis（octanureido）toluene （BSUT-8）had the best gelation abilities. The results showed that the mean minimum gelconcentrations （MGC） rose up as follows: BSDE-8, BSDM-8 and BSUT-8. The T_GS felldown as follows: BSDE-8, BSDM-8 and BSUT-8. The polarized optical microscopy imageof [bmim]PF₆ gels revealed the formation of spherical crystallites resulting from thefibrillar aggregates of the gelators.3. Linera sweep、cyclic voltammograms and impedance spectra were used to get theelectrochemical abilities of the three ionic liquids supramolecular gels. The gels hadelectrochemical stability and a wide electrochemical window. The cyclic voltammogramsof the [bmim]PF₆ gels indicate a good electrochemical stability over the range from -2.6 to2.6 V. The impedance spectra of the [bmim]PF₆ gels show good linear relationshipsbetween ion conductivity and temperature, indicating that the temperature dependence ofthe conductivity follows the classical Arrhenius equation. [bmim]PF₆ gels formed byBSDE-8 limited oxidation currents were detected in particular when potentials larger than1.5 V were applied. These oxidation currents can be ascribed to the ether group （-O-） inthe molecular structure of BSDE-8, which is easily oxidated in case of high potentials. Theion conductivities of the [bmim]PF₆ gels were found to be similar to those of the pure[bmim]PF₆, indicating that the supramolecular structures in the [bmim]PF₆ gels haveapparently no effect on the mobility of the ions. The proposed ionic liquid gels possess apotential to provide solid-like materials for the applications of electrolytes.4. The macroproperties of the three ionic liquids supramolecular gels with differentconcentrations were characterized by rheological measurements of the scillatory shear. Allthe gel samples showed similar rheological behavior. Over the range from 0.1 to 10 Hz,both the storage modulus （G′） and loss modulus （G″） were nearly frequency-independent,and G′was higher than G″. The complex viscosityη^* were decrease when the frequency increased. These results indicated that the gels were highly viscoelastic. The storagemodulus G′characterized the strength of gels, which estimated the degree of resistanceagainst mechanical stress.The tanδwere less than 1 in the whole sweep rangs, tanδdecreased first and then increased when the frequence increased. The storage modulus （G′）and loss modulus （G″） showed the same changes when the temperature increased. Thecomplex viscosityη^* were increased when the temperature increased. The tanδwere lessthan 1 in the whole temperature rangs, tanδincreased first and then decreased when thetemperature increased. With an increase of the gelators concentrations from lower to higher,the G′increased gradually, implying that three-dimensional networks became much denserwith an increase of the gelator concentrations, so both the stability and strength of the ionicliquid gel networks increased. The structures of gelators had an important effect on therheology abilities.更多还原