【作者】 朱森；

【导师】 于九皋； 程发；

【作者基本信息】 天津大学 ， 应用化学， 2007， 博士

【摘要】 表面活性剂由于其结构的特殊性,容易在表（界）面吸附,结果降低了表（界）面张力,改变了体系的表（界）面化学性质,从而表现出多种的应用功能。而Gemini表面活性剂的两个亲水离子头基是通过化学键连接,加强了碳氢链间的疏水结合力,且离子头基间的排斥倾向受制于化学键力而大大削弱,因此具有比传统的单基表面活性剂更高的表面活性。本文对于合成出的一系列Gemini阴离子表面活性剂分别研究了临界胶束浓度、表面张力和胶束聚集数等一系列基本物化性能;通过QSAR研究了临界胶束浓度和分子结构之间的构效关系;用耗散颗粒动力学（DPD）方法研究了Gemini表面活性剂在水溶液中形成有序聚集体的微观形貌,主要内容及结论如下:1、通过电导率法研究了Gemini表面活性剂的临界胶束浓度（cmc）。结果表明,其cmc比传统阴离子表面活性剂降低一个数量级左右,显示了很高的表面活性;对于同种性质的连接基,随着其长度的增加,cmc呈减小的趋势;而对于长度相同性质不同的连接基,具有亲水、柔性连接基的Gemini表面活性剂比具有刚性、疏水连接基的有更低的cmc;研究了Gemini表面活性剂的胶束形成热力学,结果表明,所研究的Gemini表面活性剂的胶束生成Gibbs自由能ΔG_mic皆为负值,显示了胶束的自发形成趋势,而ΔG_mic随着连接基的变化趋势与临界胶束浓度的测量显示了很好的一致性;C20的测量结果显示了Gemini表面活性剂突出的降低水的表面张力的效率。2、利用稳态荧光猝灭法研究了一系列Gemini表面活性剂的胶束聚集数。结果表明,对于相同性质的连接基,随着长度的增加,胶束聚集数减小;对于连接基长度相同,而具有柔性、亲水性质的连接基的Gemini表面活性剂在形成胶束时更容易紧密排列,有更大的聚集数;我们可以通过改变连接基的性质,获得具有不同聚集性质的胶束来适应不同的用途。3、利用动态光散射研究了Gemini表面活性剂在水溶液中胶束的粒径大小与分布。结果表明,具有短的连接基的Gemini表面活性剂具有较大的粒径,且为双峰,表明溶液中有不同形状的胶束共存,而具有较长连接基的Gemini A3的粒径分布为单峰,表明其仅仅形成球形胶束,即长的连接基不利于胶束的长大;利用冷冻蚀刻-透射电子显微镜（Cryo-TEM）对GeminiA3在水溶液中胶束的微观形貌进行了初探。结果表明,在低浓度时,观察不到胶束的形成,随着表面活性剂浓度的增加,逐渐观察到有球形胶束形成;且在很宽的浓度范围内皆形成球形胶束,说明了长连接基不利于胶束的长大,这与动态光散射的测量结果相一致,也说明了利用Cryo-TEM来研究此类Gemini表面活性剂在水溶液中胶束微观形貌的可行性。4、利用QSAR方法研究了Gemini表面活性剂的临界胶束浓度与表面活性剂结构之间的构效关系,分别用PCR-PLS和GFA两种回归模型建立了回归方程。结果表明,二种方法所得的模型方程都具有较高的精度,而通过遗传算法所得方程比PLS回归方程具有更高的精度和更强的预测能力,说明通过QSAR方法可以达到准确预测具有相似结构的Gemini表面活性剂溶液性质的目的,为具有更好表面活性的Gemini分子的合成提供指导。5、通过耗散颗粒动力学（DPD）方法对Gemini表面活性剂在水溶液中的聚集形态进行了模拟,DPD模拟的结果表明,在很低的浓度下,溶液中首先形成胶束预聚体,随着浓度的增加,逐渐形成球形胶束,继续增加浓度,球形胶束长大成为花生状胶束并进一步长大为棒状胶束;在更高的浓度下,棒状胶束相互交联形成层状相,且发现与传统的表面活性剂溶液不同,在胶束和层状相之间没有出现过渡的六方相结构;由于DPD方法采用了简化的DPD粒子模型,因此可以抓住此类双亲分子的主要结构特点,模拟体系的直观结果可以和实验结果相互印证,为设计实验方法提供理论的指导。更多还原

【Abstract】 The surfactants are readily to adsorb at the surface for its special structure and reduce the surface tension. So they can change the character of the surface and put up a lot of applications. As the head groups in Gemini surfactant are connected by chemical bond and strengthen the hydrophobic effect between hydrocarbon chains, it has much higher surface activity than conventional ionic surfactant. In this paper, some basic characters including cmc, surface tension and aggregation number of a series of anionic Gemini surfactants have been investigated. The relationship between critical micelle concentration and molecular structure has been studied by Quantum Structure–Active Relationship （QSAR） method. And Dissipative Particle Dynamics （DPD） has been employed to study the microstructures of aggregates of Gemini surfactant in aqueous solutions.The overall results are shown below:1 The critical micelle concentration of Gemini surfactants has been studied by electrical conductivity method. Results showed that Gemini surfactants have much higher surface activity than traditional ionic surfactants. Cmc decreases with the increase of the spacer chain length for the spacer having almost the same nature. For the spacer has almost the same length but different nature, the surfactant with the flexible, hydrophilic spacer has the lowest cmc value. Calculation of the standard free energy (ΔG_mic ) of micellization is consistent with their tendency to form micelles in solution and negativeΔG_mic values suggested that the Gemini surfactants have great ability to form micelles in solution. C20 values show that it is more efficient in declining surface tension of the water.2 The steady fluorescence quenching method has been used to study the aggregation numbers （N） of Gemini surfactants in aqueous solutions. Results showed that the longer the spacer chain, the smaller the aggregation number for the same spacer nature and the Gemini with the flexible, hydrophilic spacer has the largest N for almost the same spacer length. The Gemini surfactant with hydrophilic, flexible spacer can form a well-packed micelle. Therefore, it offers us the probability to obtain Gemini surfactants with different aggregation properties by changing the nature of the spacer to need our different uses.3 The micellar growth of Gemini surfactants containing oxyethyl group spacer in aqueous solutions has been studied using dynamic light scattering. The size of the micelles increases with decreasing the length of the spacer chain, which suggested that long spacer chain prevents the growth of micelle. Transmission electron microscopy at cryogenic temperature （cryo-TEM） was extensively used to investigate the microstructure of Gemini surfactant in aqueous solutions. The cryo-TEM studies showed that with increasing the concentration, spherical micelle could be seen and it can exist in a very broad concentration range.4 The relationship between cmc and surfactant structure has been studied using QSAR models and regression models were built up by principle component analysis-partial least squares （PCR-PLS） and genetic function approximation （GFA） respectively. Results showed that the GFA models has much higher precision and predictive capacity and it suggests that QSAR methods can give us probability to predict the character of aqueous solutions of Gemini surfactants with almost the same structure and give guidance to the synthesis of newly Gemini surfactants with higher activity.5 The microstructure of aggregates of Gemini surfactants in aqueous solutions was investigated by dissipative particle dynamics （DPD） simulation. We found that DPD simulation can look into the assemble process. With increasing the concentration of Gemini surfactant, the aggregates can form different structures: spherical micelle, peanut micelle, mixed micelle of sphere and rod, rod-like micelle and lamellar phase. As predigested DPD particles （beads） are employed in DPD simulation, it can hold up the main structure characteristic of these amphiphile and compare with the results of experiments and give advices to the design of the experiments.更多还原