【作者】 杨红伟；

【导师】 吴大诚；

【作者基本信息】 四川大学 ， 材料学， 2006， 博士

【摘要】 双子表面活性剂是通过一个连接基将两个传统表面活性剂分子在其头基或接近头基处连接在一起而形成的一类发展较快的新型表面活性剂。与传统表面活性剂相比，双子表面活性剂具有更高的表面活性，能更有效的降低溶液的表面张力，更容易聚集生成胶束，具有较低的Krafft点，优良的润湿性能等，已成为国际胶体科学领域和工业应用的研究热点之一。季铵盐双子表面活性剂是一种目前研究较多的、重要的阳离子双子表面活性剂。与单季铵盐相比，双季铵盐具有更高的表面活性、更强的杀菌性能、生物降解性好、毒性低等优异的性能。当前，限制双子表面活性剂大规模应用的主要因素是其昂贵的价格，而与合适的廉价表面活性剂复配可能会产生明显的协同效应，因此探索双子表面活性剂与普通表面活性剂进行复配使用，研究它们混合体系的表面性质已经受到人们的广泛关注。近年来，利用Langmuir膜天平研究双子表面活性剂单分子膜在界面上的吸附行为，并借助先进的仪器观察它们聚集形态，这在表面科学中具有重要的理论和实际意义。LB膜技术是获得超薄有序分子膜的一个有效手段，可以实现分子水平上的组装，能制备厚度精确可控、结构明确、各向异性的单分子膜和多层膜，是目前人们所能制备的最紧密、缺陷最少的超分子薄膜。Langmuir膜天平是制备LB膜常用的仪器，也是研究分子的尺寸和排列方式的一种重要方法。早在20世纪30年代，科学家们用它来研究小分子的单分子膜及LB膜，但因小分子LB膜的耐热性和力学强度差，限制了其应用。后来，人们开始研究聚合物单分子膜和LB膜，并取得突破性进展。近年来，由于聚氧乙烯（PEO）具有表面活性、生物可降解性、无毒等特点，在生物技术和医学材料上有着广泛应用，因此利用Langmuir膜天平研究含有PEO的接枝、嵌段和星型共聚物单分子膜在界面上的表面性质、聚集形态已经引起人们的研究兴趣。本论文利用Langmuir膜天平主要研究了季铵盐双子表面活性剂以及含PEO的两亲性嵌段聚醚酯在空气—水界面上的单分子膜。从季铵盐双子表面活性剂单分子膜的π-A等温线分析了它们在界面上的构象，并且通过它们的静态弹性、动态弹性，进一步讨论了分子间的排列情况。为了寻找一种合适的表面活性剂与季铵盐双子表面活性剂复配，以期达到双子表面活性剂广泛应用的目的，我们又研究了季铵盐双子表面活性剂与其它表面活性剂的混合单分子膜。以混合膜的π-A等温线为基础，与对应的普通表面活性剂相比较，讨论了混合膜的平均分子面积与理想混合膜的偏差，表面过剩混合自由能以及相互作用参数，分析了混合膜的相容性。最后研究了不同硬链段比例的含PEO两亲性嵌段聚醚酯在空气—水界面上单分子膜的π-A等温线，随着嵌段聚醚酯硬链段比例的增大，单分子膜的凝聚性增强，比较了这些两亲性嵌段聚醚酯单分子膜的静态弹性和动态弹性，并且讨论了它们在不同表面压下的循环曲线、表面压与时间的变化关系，揭示它们单分子膜的稳定性，提供了制备LB膜的基础。本论文的主要研究工作为：1．首先研究了非离子表面活性剂脂肪醇聚氧乙烯醚(C₁₈E₂₀)分别与三种长链脂肪醇（正辛醇、十二醇、十八醇）在空气—水界面上混合膜的π-A等温线。通过比较不同摩尔比的C₁₈E₂₀与脂肪醇混合膜的π-A等温线，分析了它们在空气—水界面上混合膜的凝聚性。结果表明，在C₁₈E₂₀中加入脂肪醇可以改变单分子膜的凝聚性，并且加入脂肪醇的摩尔分数越大，混合膜的稳定性越强。这是由于C₁₈E₂₀的疏水碳链为C₁₈，混合膜中脂肪醇的碳原子数与C₁₈E₂₀的疏水链相近程度越高，则混合膜越凝聚。当十八醇与C₁₈E₂₀的摩尔比大于3：1混合时，混合膜在高表面压下显示为较好的相容性。2．着重研究了季铵盐双子表面活性剂12-2-4、12-2-8、12-2-12、12-2-16以及传统阳离子表面活性剂DTAB在空气—水界面上形成单分子膜的π-A等温线。实验结果表明，12-2-8、12-2-12、12-2-16比DTAB单分子膜的分子极限面积大，12-2-4的分子极限面积接近DTAB的，并且双子表面活性剂的崩溃压高于DTAB的。这意味着单分子膜在凝聚态时分子的构象不同，12-2-4的一条疏水链浸入水中，另一条疏水链直立在水面上，与DTAB的取向相似，而12-2-8、12-2-12、12-2-16的两条疏水链脱离水面，朝向空气，呈“U”型构象。它们单分子膜的静态弹性大小依次为12-2-4＜12-2-8＜12-2-12＜12-2-16，表明双子表面活性剂的静态弹性与它的疏水链长度有关，即疏水链越长它的静态弹性越大。同样，季铵盐双子表面活性剂12-2-4、12-2-8、12-2-12、12-2-16单分子膜的动态弹性大小依次为12-2-4＜12-2-8＜12-2-16＜12-2-12，并且12-2-4的动态弹性与DTAB的基本相同，这与双子表面活性剂分子在界面上的构象、排列紧密程度有关。此外，简单讨论了三聚表面活性剂12-2-12-2-12单分子膜的π-A等温线、静态弹性以及动态弹性，与12-2-12、DTAB相比，12-2-12-2-12的分子极限面积大于12-2-12、DTAB的，但是在高表面压下静态弹性、动态弹性却小于12-2-12、DTAB的，表明在单分子膜的凝聚态时，12-2-12-2-12分子的紧密排列程度不如12-2-12、DTAB的。3．主要研究了对称双子表面活性剂12-2-12、不对称双子表面活性剂12-2-16及DTAB分别与非离子表面活性剂脂肪醇聚氧乙烯醚(C₁₈E₂₀)在空气—水界面上形成的混合膜。与DTAB混合膜的π-A等温线相比，12-2-12、12-2-16分别与C₁₈E₂₀混合膜的液态扩张性增加。通过比较不同表面压下混合膜的平均分子面积与理想曲线的偏差，以及混合表面过剩自由能和相互作用参数，分析了混合膜的相容性。其结果表明，双子表面活性剂12-2-12、12-2-16比DTAB有较高的崩溃压，说明12-2-12、12-2-16在空气—水界面上存在较强的分子间相互作用，单分子膜中同种分子间相互作用的强度次序为12-2-16＞12-2-12＞DTAB。当它们与C₁₈E₂₀分别组成混合膜时，除了C₁₈E₂₀摩尔分数为0.9及低表面压的少数情况外，一般引起混合膜的扩张，即混合膜中分子间的相互作用参数为正值。这种差别是由于阳离子表面活性剂分子间存在较强的相互作用，在较高表面压和较高摩尔分数双子表面活性剂的情况下，插入具有长链亲水基的非离子表面活性剂，可能打乱了同种阳离子表面活性剂之间的紧密排列，使混合表面过剩自由能增大，这种影响的大小与同种阳离子表面活性剂分子之间的相互作用强度次序一致。4．DTAB、12-2-12和12-2-16分别与十八醇(C₁₈H₃₇OH)在空气—水界面上形成的混合单分子膜。通过比较不同表面压下混合膜的平均分子面积与理想曲线的偏差，以及混合表面过剩自由能和相互作用参数，分析它们在界面上混合膜的相容性。其结果表明，在C₁₈H₃₇OH摩尔分数为0.9的DTAB混合膜和C₁₈H₃₇OH摩尔分数为0.7～0.9的12-2-12混合膜，以及在C₁₈H₃₇OH与12-2-16任意摩尔比的混合膜中，分子之间的相互作用参数均为正值。这是由于十八醇的插入打乱了同种阳离子表面活性剂之间的紧密排列，使混合表面过剩自由能增大，同样这种影响的大小与同种阳离子表面活性剂分子之间的相互作用强度次序一致。5．DTAB、12-2-12和12-2-16分别与阴离子表面活性剂十二烷基硫酸钠（SDS）在空气—水界面上形成混合单分子膜。在SDS摩尔分数为0.1～0.3时，DTAB与SDS混合膜的凝聚性增加，12-2-12、12-2-16分别与SDS混合膜的扩张性比各自的对应的双子表面活性剂单分子膜的凝聚性减弱；在SDS摩尔分数为0.7～0.9时，DTAB、12-2-12、12-2-16分别与SDS混合膜的凝聚性增强。这不仅与三种阳离子表面活性剂同种分子间的相互作用力，混合表面活性剂中离子间的相互吸引力有关，而且主要受混合膜中过剩离子的影响。因此DTAB与SDS混合膜的复配能力大于12-2-12与SDS或12-2-16与SDS混合膜的，并且12-2-12与SDS混合膜的复配能力大于12-2-16与SDS混合膜的。6．研究了几种不同硬链段比例的两亲性嵌段聚醚酯在空气—水界面上形成单分子膜的π-A等温线。简化了含PEO的两亲性嵌段聚醚酯在界面上PEO亲水链的复杂变化，主要讨论了两亲性嵌段聚醚酯的疏水硬链段的π-A等温线，并且计算了硬链段的理论面积；通过分析不同硬链段比例对两亲性嵌段聚醚酯单分子膜π-A等温线的影响，表明随着硬链段比例的增加，聚醚酯单分子膜的凝聚性增加。从聚醚酯单分子膜的表面压与时间的变化关系可以看出，聚合物单分子膜中大分子链的松弛变化。这几种两亲性嵌段聚醚酯的静态弹性、动态弹性变化趋势基本一致，而硬链段为50％的聚醚酯单分子膜的动态弹性较大，说明硬链段间的相互作用较大，受到扰动后，抗形变能力较强。更多还原

【Abstract】 Of the newly developed surfactants, gemini surfactants consist of two hydrophobic chains and two hydrophilic groups covalently attached through a spacer. Gemini surfactants have superior performances over their corresponding conventional surfactants, such as much lower critical micelle concentration, higher efficiency in reducing surface tension, much easier forming into micelle, lower Krafft point, much better wetting ability and so on. Recently, gemini surfactants have become a hot topic of colloid science and industry in the world due to their unusual properties and potential applications, in which quaternary ammonium gemini surfactants are important cationic surfactants. In comparison with the conventional single-chain surfactants, quaternary ammonium gemini surfactants have prominent characters, such as higher surface activity, more strong sterilization ability, better biodegradation ability, lower toxicity etc., so various academic groups worldwide have continued the synthesis, characterization of structure and physicochemical properties. Gemini surfactants are very expensive, so the large scale application is restricted. A practicable solution to this problem is to compound other surfactants with gemini surfactants, so that it could produce obvious synergistic effect. Therefore extensive attention has been paid for the surface properties of the mixed system between gemini surfactants and other surfactants. The behavior of monolayers for gemini surfactants have been investigated at the interface by use of Langmuir balance, and the aggregation morphology have been observed in virtue of the advanced instruments. It is important of theoretical and practical signification in surface science.LB membrane technology is an effective method of obtaining orderly molecular ultra thin film. It can assemble on the level of molecule and can prepare monolayer or multilayer that the thickness is exact controlled and the structure is definitive and the property is anisotropic. LB film is the tightest and almost disfiguration-free ultrathin molecular film prepared for the moment. Langmuir balance is not only the most common instrument in preparing LB film, but also an important means researching the molecular dimension and arrangement mode. Many scientists studied monolayer and multilayer of small molecule since 1930. But for small molecules the heat resisting property and mechanical strength of LB are not good, so the application is limited. Monomolecular film and LB membrane of polymer have also been investigated, and it has been made a scientific breakthrough. Among amphiphilic polymers, polyethylene oxide （PEO）s are of biodegradability and surface activity, and it is extensively applied in biotechnology and medicine material. Recently the surface behavior and aggregation morphology of monolayers for graft, block and star copolymers containing PEO at interface have been extensively and intensively studied.In this article monolayers of quaternary ammonium gemini surfactants and amphiphilic block copolymers containing PEO were formed at air-water interface using Langmuir balance. The molecular conformation of quaternary ammonium gemini surfactants was analyzed by theπ-A isotherms of monolayers, and the monolayer stability was further discussed by way of the static or dynamic surface elasticity. The mixed monolayers for quaternary ammonium gemini surfactants with other appropriate surfactants were explored in order to research their compounded ability. Based on theπ-A isotherms, the deviation of the mean molecular area from ideal curves, mixed surface excess free energy and interaction parameters of each mixed monolayer at different surface pressure were analyzed, and the feature of monolayers at air-water interface was discussed. Furthermore, the monolayers for amphiphilic block copolymers containing PEO with different proportional hard segments were investigated at air-water interface. It was found from theπ-A isotherms that the cohesion of monolayer is increased with the proportion of hard segments in amphiphilic block copolymer. The static and dynamic surface elasticity of monolayers for amphiphilic block copolymers were compared, and the cyclic curve at different surface pressure, the relationship between surface pressure and time were discussed. The highlight of results in the paper is as follows:Poly（ethylene oxide） alkyl ether, C₁₈E₂₀, was in combination with each of three n-fatty alcohols （1-octanol, n-dodecanol and n-octadecanol） respectively as a model of nonionic surfactant and polar organic substance composites, which was spread onto air-water interface and formed a mixed monolayer on a Langmuir trough. The stability of each mixed monolayer was analyzed by use of theπ-A isotherms at various mole fractions of the C₁₈E₂₀-fatty alcohol pair. It was found that the C₁₈E₂₀ monolayer exhibits characters of a liquid expanded monolayer, with a collapse pressure 30 mN/m. The stability of the C₁₈E₂₀ monolayer could be enhanced by combining with fatty alcohols, based on two points. The one is the expanding degree of the monolayer decreases as the surface pressure of the mixed monolayer is under the inflexion of theπ-A curve, and the other is that the plateau length of the curve decreases after the surface pressure is above the inflexion of theπ-A curve, comparing with the pure C₁₈E₂₀ monolayer. The condensability of the mixed monolayer increases with the mole ratio of fatty alcohol, and with the hydrophobic chain length of the alcohol up to that of C₁₈E₂₀. For almost all of theπ-A isotherms of the mixed monolayers, the inflexion and the plateau always appeared near the surface pressure 30 mN/m, which showed that a phase-separation occurs for the mixed monolayer at a higher surface pressure corresponding the collapse pressure point of C₁₈E₂₀. It was also observed that the mixed monolayer is in a favorable condition for the compatibility of the compounded surfactants, as the mole ratio of C₁₈E₂₀ and n-octadecanol is equal to 3:1.Quaternary ammonium gemini surfactants 12-2-4, 12-2-8, 12-2-12, 12-2-16 and corresponding conventional surfactant, dodecyl-trimethylammonium bromide （DTAB） were spread onto air-water interface, respectively, forming monolayer in KSV Langmuir trough. It was found that the molecular limited areas of 12-2-8, 12-2-12, 12-2-16 in each monolayer are greater than that of DTAB, but the molecular limited area of 12-2-4 is similar to DTAB, and that the collapsed surface pressures of gemini surfactants are higher than that of DTAB. It means that the molecular conformation of monolayer is different. For 12-2-4 the shorter hydrophobic chain may be under the water, but the other one may be perpendicular away from the water; the orientation of 12-2-4 is similar with that of DTAB. In contrast, for 12-2-8, 12-2-12 and 12-2-16, the two hydrophobic chains seem to break away water, and appear "U" conformation. The static surface elasticity of gemini surfactants are in turn of 12-2-4 < 12-2-8 < 12-2-16 < 12-2-12, moreover it is indicated that the static surface elasticity of gemini surfactants is relate to the length of hydrophobic chains, and that the greater the length of the hydrophobic chain is, the higher the static surface elasticity. The order of dynamic surface elasticity of gemini surfactants measured by the barrier oscillation method is: 12-2-4 < 12-2-8 < 12-2-16 < 12-2-12, with the similar values for 12-2-4 and DTAB.Mixed monolayers formed using a symmetric gemini surfactant 12-2-12, a dissymmetric gemini surfactant 12-2-16 and DTAB with C₁₈E₂₀ at air-water interface were investigated by a Langmuir trough. It was found from theπ-A isotherms for mixed monolayers that the expanding liquid state arises from the steric effect in the hydrophilic long chain of C₁₈E₂₀. The mean molecular area, mixed surface excess free energy and interaction parameters of each mixed monolayer at different surface pressure were analyzed. It is shown that each of mixed monolayers is miscible, and the positive interaction parameters of mixed monolayers for gemini surfactants with C₁₈E₂₀ are greater than those of mixed monolayers for DTAB and C₁₈E₂₀. It is also shown that the repulsion interaction between gemini surfactant and C₁₈E₂₀ in the mixed monolayer is strong at air-water interface, and the interaction intensity of mixed monolayers with C₁₈E₂₀ is in turn of 12-2-16 > 12-2-12 > DTAB.Mixed monolayer formed by each of 12-2-12, 12-2-16 and DTAB with octadecyl alcohol (C₁₈H₃₇OH) spread onto air-water interface was investigated with a Langmuir trough. It was found from theπ-A isotherms for mixed monolayers that the condensed state arise from the incorporation of C₁₈H₃₇OH. The mean molecular area, mixed surface excess free energy and interaction parameters of each mixed monolayer at different surface pressure were analyzed. It was shown that each of mixed monolayers was partly miscible, and the interaction parameters of mixed monolayer for gemini surfactants with C₁₈H₃₇OH were almost positive values greater than those of monolayers for DTAB with C₁₈H₃₇OH. It was also shown that the repulsion interaction between gemini surfactant and C₁₈H₃₇OH in the mixed monolayer was strong at the air-water interface, and the interaction intensity of mixed monolayers with C₁₈H₃₇OH is in turn of 12-2-16 > 12-2-12 > DTAB.Mixed monolayer formed by each of 12-2-12, 12-2-16 and DTAB with lauryl sodium sulfate （SDS） spread onto air-water interface was studied. When the mole fraction of SDS is 0.1～0.3, the cohesion of mixed monolayers for DTAB and SDS is stronger than that of DTAB, but the expanded state for mixed monolayers of 12-2-12 / SDS and 12-2-16 / SDS are increased in comparing with the corresponding gemini monolayers. As the mole fraction of SDS is within 0.7～0.9, the cohesion of each mixed monolayer for the three cationic surfactants with SDS is increased, respectively. It is related not only to the static attraction between anionic and cationic surfactants, but also to the reciprocity of homogeneity of molecules for three cationic surfactants. It was shown that the compounded character of mixed monolayers with SDS for the three cationic surfactants is 12-2-16 > 12-2-12 > DTAB.The monolayers for amphiphilic block copolymers containing PEO with different proportional hard segments were investigated at air-water interface. Theπ-A isotherm of hydrophobic hard segments in an amphiphilic block copolymer was discussed in case of ignoring the complex change for hydrophilic PEO chains at/or under the interface, and the theoretic area of hard segments was calculated. It was found from theπ-A isotherms that the cohesion of monolayer is strongly increased with the proportion of hard segments. The chain relaxation changes of monolayer can be seen from the relationship between surface pressure and time. The static surface elasticities of monolayers for amphiphilic block copolymers were similar each other, but for that of copolymer with 50% hard segments one little peak appears before the monolayer collapsed. Moreover, the cyclic curve at different surface pressure, the relationship between surface pressure and time were discussed. The dynamic surface elasticity of amphiphilic block copolymer with 50% hard segments is higher than those of other copolymers, which means that the reciprocity of hard segments is greater, so does the resisting distortion ability as the monolayer is interfered.更多还原