【作者】 黄涛；

【导师】 游毅；

【作者基本信息】 福州大学 ， 有机化学， 2005， 硕士

【摘要】 二聚表面活性剂是将两个单链单头基普通表面活性剂在离子头基处通过联接基团用化学键联接起来所形成的。联接基团的引入,使有效的调控离子头基之间的距离成为可能,从而使它表现出优良的表面活性和丰富多样的分子有序聚集体形状与特性,是目前胶体与界面化学领域的研究热点。由单分子膜制备而成的LB 膜是具有分子排列高度有序且层结构各向异性的特点,能在分子水平上对材料进行控制性组装,这使LB 膜在半导体技术、非线性光学材料、仿生材料等高技术领域具有广阔的应用前景。二聚表面活性剂在气/液界面上表现出来的独特的性质,使这种结构新颖的表面活性剂应用到LB 膜领域,进行功能材料的开发成为可能。在本文中设计并合成了一种新型结构的多疏水链阳离子二聚表面活性剂,并测定了它所形成的不溶单分子膜在不同条件下的π-A 等温线。实验中通过双十二烷基甲基叔胺与α,ω-二溴代烷以3∶1 的投料比,在无水乙醇中回流48 小时,再经重结晶后,得到了一系列不同长度碳氢链长和联接链长的多长链季铵盐型二聚表面活性剂,通过~1H NMR 、IR、元素分析验证了它们的结构。在不同条件下测定了合成目标产物形成的不溶膜的π-A 等温线,发现1)分子结构的改变会对它所形成的单分子膜性能产生很大的影响。当碳氢链长度增加时,π-A 等温线越趋向于凝聚,由液相向固相的转变越不明显,同时膜的崩溃压升高,表明膜的强度有所增加;当联接链长度增加时,π-A 等温线越趋向于扩张,同时分子极限占据面积也随之增加。2)亚相成分的改变也会使它的成膜性质发生很大的变化。当亚相为0.01M NaBr 溶液时,膜的π-A 等温线更凝聚;同时还发现它得到的崩溃压相对于纯水作亚相π-A 等温线的崩溃压的差值随联接链碳原子数的减少而增大;另外膜的分子极限占据面积有逐渐趋于一致的倾向。这些现象都是由于亚相中大量存在的溴离子会由于浓度较高而进入离子表面活性剂本身的反离子所形成的扩散双电层,并压缩不溶膜的双电层而产生的结果。另外,在研究温度对它的曲线影响时发现,温度对合成的二聚表面活性剂成膜的影响很小,而这种结构的单体受温度的影响非常明显。以上这些结果都说明我们合成的这种新型结构表面活性剂具有良好的成膜性更多还原

【Abstract】 Gemini surfactants are made up of two identical amphiphilic moieties covalently connected at the level of the headgroups by a spacer group, The introduce of spacer group made it possible to efficient control the distance of headgroups. And this make it exhibit excellent surface activity and interesting rheological properties, Owing to this, it have attracted considerable attention in colloid and interface chemistry domain. Langmuir-Blodgett film which made from monolayer films is highly ordered in molecular scale and form laminar structure with anisotropy, Could fabricate multilayer in a molecular scale and with controllable. And this made it have a broad application foreground in high-technological fields, such as semiconductor, nonlinearoptics, bionics and so on. Gemini surfactants exhibited unique properties on gas/liquid surface. And this makes it possible to apply this novel structure amphiphilic moieties to LB film domain for the purpose of new functional material exploit. A series of different alkyl length and spacer length multialkyl cationic Gemini surfactant was designed and synthesized in this article, And pressure-area isotherms of it’s monolayer film was measured under different condition. Methyldidodecylamine and α,ω-dibromoalkane was mixed with the molar ratio of 3:1 in ethanol and reflux for 48h, recrystallized for several times,then a series of Multialkyl cationic Gemini Surfactants was synthesized. The structures were confirmed by IR, ~1H NMR, elemental analysis. The pressure-area isotherms was measured of this compounds under different condition, it shows: i. The change of molecular structure have a great effect on the property of it’s monolayer. As the length of alkyl-chain increased, π-A isotherm has a more condensed tendency,the transition from liquid phase to solid phase is less clear and the collapse pressure of film increased which indicates strength of film increased; As spacer length increased, π-A isotherm has a more expanded tendency, and the extrapolated molecular area increased at the same time. ii. The substance of subphase also causes great effect on its film. When use 0.01mol?L-1 NaBr as subphase , the π-A isotherm of film was more condensed; we also compared the collapse pressure on salt solution and on pure water as subphase, find the difference increased as the number of carbon atom of spacer decreased; and the extrapolated molecular area consistent with each other. All of these changes are caused by the fact that large amount of bromide ion exist in subphase should penetrate into the diffusion layers formed by counter ion of ionic surfactant because of the concentration degree, and compressed the diffusion layers of insoluble film. And in the process of research for temperature effect on π-A isotherm, it’s proved that temperature has a little effect on the insoluble films of synthesized dimeric surfactants. But it has a great effect to the monomer of the surfactants. All of this proved the novel structure surfactant has a good ability to form films, and we can adjust the molecular structure and external condition to get the best method for the deposition process of LB films. And it’s an ideal material to form LB films.更多还原