【作者】 陈万煜；

【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， 2008， 博士

【摘要】 离子键交联凝胶是一种新型的在非共价作用下形成的凝胶,它以聚合物链上的正负离子基团间的静电引力形成离子交联键。本文以丙烯酸（AA）和甲基丙烯酸二乙胺基乙酯（DEAM）形成的离子复合物和丙烯酰胺（AAm）为单体,在水或有机电解液中采用自由基聚合制备了一系列新型的离子键交联聚两性电解质凝胶（PADA凝胶）。在水中合成得到的PADA水凝胶的非接触直流电场的实验表明该离子键交联的PADA凝胶在电场下发生溶蚀现象。PADA凝胶的溶蚀速率与电场强度、溶液浓度、pH值、酸碱基团摩尔比、溶液离子价态等诸多因素有关,如溶蚀随电压的升高而增大,随盐溶液浓度的加大而增大。其溶蚀动力学研究表明PADA凝胶的溶蚀度随时间线性的增加,即溶蚀速率在整个实验时间内基本保持恒定。在含1mol/L的LiClO₄的碳酸丙烯酯（PC）溶液或体积比为3:1:1的PC:甲乙醚（DOL）:二氧戊烷（DME）混和溶液（以下简称为PDD溶液）中制备的PADA有机凝胶电解质的热学性能测试表明该凝胶具有很好的热学稳定性,并且交流阻抗研究表明在-30℃到75℃温度范围内,两类PADA凝胶电解质的离子电导率大小与液体电解质的电导率很接近,电导率与温度的关系遵循阿累尼乌斯方程。在相同温度下,以粘度较小的PDD为溶剂制得的PADA凝胶电解质的电导率高于以PC为溶剂制得的PADA凝胶电解质,且电导率随温度的变化也较小。在PC和PDD溶剂中制备的两类PADA凝胶的电导率都随着正负离子单体比增大而增大。循环伏安法研究表明PADA凝胶电解质在-1V-4.5V间能保持稳定的电化学性能。在含1mol/L LiPF₆的乙烯碳酸酯（EC）、二甲基碳酸酯（DMC）和乙基甲基碳酸酯（EMC）（体积比为1:1:1）的混合有机溶剂中制备得到的PADA有机凝胶电解质的交流阻抗研究表明该凝胶的离子电导率与液体电解质的电导率很接近,其电导率与温度的关系遵循阿累尼乌斯方程。通过交流阻抗分析、循环伏安分析以及扫描电镜方法分析了由凝胶电解质所形成的SEI膜。研究表明PADA有机凝胶电解质能在最初的几次充放电循环后生成致密的SEI膜,但与溶液电解质形成的SEI膜在微观形态上有所不同,主要由一些较小的固体物堆积形成,表面不够平整,并在随后的循环中变得更致密。二（对甲基苄叉）山梨醇（MDBS）是一种能使众多有机溶液凝胶的凝胶因子。本文研究了不同浓度（2—7 wt%）的二（对甲基苄叉）山梨醇（MDBS）在碳酸丙烯酯（PC）中形成的有机凝胶体系在一系列尺度在20到80μm的微通道中的自组装行为,探讨了空间限制对有机凝胶因子自组装的影响和在受限空间中生成的有机凝胶的性质。光学显微镜、偏光显微镜、扫描电镜（SEM）和透射电镜（TEM）结果表明当凝胶因子MDBS浓度一定时,MDBS/PC凝胶的微观结构随着微通道宽度的增大而由纤维网络结构转变为球状结构;当微通道宽度一定时,凝胶的微观结构随着MDBS浓度的增大而由纤维网络结构转变为球状结构。对从微通道中取出的已完成自组装的MDBS/PC凝胶进行光学显微镜分析和和差示扫描量热分析（DSC）表明在受限空间中生成的凝胶的纤维网络结构在被从微通道中取出后仍能保持稳定。我们的研究表明可以通过改变凝胶因子的浓度和微通道的尺度来调控凝胶的微观结构,并进而改变凝胶的热学性能。更多还原

【Abstract】 Ionically crosslinked gels are novel non-covalent bond gels.The electrostatic attraction of high density between negatively and positively charged groups on polymer chains makes the polymer chains capable to form stable junction zones which maintain the ordered structure inside the ionically crosslinked gels.An ionic complex of anionic and cationic monomers was obtained by protonation of（N,N-diethylamino）ethylmethacrylate （DEAM） with acrylic acid（AA）.Free radical copolymerization of the ionic complex and acrylamide（AAm）,yielded the ionically crosslinked polyampholytic gel electrolytes [poly（AAc-DEAM-AAm）,designated as PADA]using water or organic solvents.The investigation indicated PADA hydrogels that were prepared in water exhibited peculiar erosion phenomenon under non-contact direct current electric fields.The erosion rate of PADA gels was related to the voltage of electric field,the concentration of salt solution,pH value of buffer solution,the molar ratio of anionic/cationic monomers,valence of ion and so on.For instance,the erosion rate increased with an increase of voltage or the concentration of salt solution.The erosion kinetics revealed that the erosion rate of PADA gels was almost invariable in experiments.The PADA organogel electrolytes that were prepared in two types of organic solvents （propylene carbonate（PC） and the mixture of PC,ethyl methyl ether（DME） and dioxolane （DOL）（3:1:1,v/v,designated as PDD）） containing a lithium salt（LiClO₄,1mol/L） exhibited good thermal stability.The impedance analysis at temperatures ranging from -30 to 75℃indicated that the ionic conductivities of the PADA gel electrolytes were rather close to those of liquid electrolytes.The temperature dependence of the ionic conductivities was found to be in accord with the Arrhenius equation.Moreover,the ionic conductivities of PADA gel electrolytes increased with an increase of the molar ratios of cationic/anionic monomers.The ionic conductivities of PADA gels prepared in PDD were higher than those of PADA gels prepared in PC only.The electrochemical windows of PADA gel electrolytes measured by cyclic voltammetry were in the range from -1 to 4.5V（vs.Li/Li⁺）.The impedance analysis of the PADA organogel electrolyte that was prepared in a solvent mixture of ethylene carbonate（EC）,dimethyl carbonate（DMC） and ethyl methyl carbonate（EMC）（1:1:1,v/v） containing 1 mol/L of LiPF₆ indicated that the ionic conductivity of the polyampholytic gel electrolyte was rather close to that of solution electrolytes in the absence of a polymer at the same temperature.The temperature dependence of the conductivity was found to be well in accord with the Arrhenius behavior. The formation processes of the solid electrolyte interphase（SEI） formed in both gel and solution electrolytes during the cycles of charge-discharge were investigated by cyclic voltammetry,electrochemical impedance spectroscopy and field emission scanning electron microscopy.The results indicate that the SEI formed in the gel electrolyte showed a rough surface consisting of smaller solid depositions.1,3:2,4-di-p-methylbenzylidene sorbitol（MDBS） is a small organic molecule that is capable of inducing self-assembly in a wide variety of organic solvents and of forming organogels.In this paper,we present a novel approach to tune the network architectures of organogels by utilizing geometric confinement while varying the gelator concentration. Self-assembly of MDBS in propylene carbonate（PC） is investigated in a series of microchannels with widths varying from 20 to 80μm and the gelator concentration varying from 2 to 7 wt%.We demonstrate by optical microscopy,scanning electron microscopy （SEM）,polarized microscopy and transmission electronmicroscopy（TEM） that a transition from fibrillar structure to sheaflike spherulite structure occurs when（a） the channel width is increased for fixed gelator concentrations and（b） gelator concentration is increased for fixed channel widths.A phase diagram is built based on these observations.The thermal properties of the organogel are measured by differential scanning calorimetry（DSC） to verify the structural difference obtained under confined and unconfined conditions and the structure stability.Our results provide a novel strategy to control the topological structure of self-assembled systems and to modify their thermal properties via geometric confinement.更多还原