【作者】 马福民；

【导师】 陈晓；

【作者基本信息】 山东大学 ， 胶体与界面化学， 2010， 博士

【摘要】 两亲分子在合适的介质中自组装形成的有序分子聚集体,如胶束、囊泡、溶致液晶和微乳液等,可广泛地应用在材料、生命、制药、分离分散、信息和能源等领域。在自组装介质方面,传统的介质主要是水和各种有机溶剂,组成的体系一般存在稳定性较低、挥发性和导电性差等缺点。因而,具有特殊物理化学性能(如低挥发性、宽电化学窗口、不可燃性和优良的热稳定性等)的离子液体在构建有序分子聚集体方面的研究引起了各国科研工作者的兴趣。近年来,合成提纯简便、易形成氢键网络的质子化离子液体作为自组装介质在这方面的研究尤其活跃。这不仅发展了有序分子聚集体的介质领域,同时为燃料电池的质子电解质、生命和催化等一些质子传导、水敏感的特殊领域提供了潜在的应用前景。在两亲分子方面,由常见的咪唑类离子液体衍生的具有两亲性的长链咪唑类化合物已被广泛地用于构建胶束、微乳液、溶致液晶及其凝胶等有序分子聚集体,并在材料制备等领域发挥着重要作用；近几年的研究表明,其它具有两亲性质的长链氮杂环化合物可表现出优异的性能,其在构建包括溶致液晶在内的新型有序分子聚集体体系方面的研究也正受到重视,这可为发展新型有序分子聚集体体系及其潜在的应用提供基础。本篇论文关注和研究的是质子化离子液体和氮杂环化合物在构建有序分子聚集体领域中的应用,中心思想是以质子化离子液体作为介质来构建新型溶致液晶体系,并考察其微结构及流变、导电等性能；合成并表征一系列的氮杂环化合物,探索其性能及其在构建有序分子聚集体方面的应用。论文的主要内容如下：第一部分介绍了当前工作的研究背景,综述了表面活性剂和离子液体的研究历程与发展状况,对质子化离子液体和氮杂环化合物在构建有序分子聚集体方面的应用进行了重点介绍,为本论文的研究提供了理论基础和技术支持。最后对本论文的立题思想、研究内容等进行了简要阐述。第二部分主要探讨了Brij 97(C18:iEO10)在质子化离子液体中的聚集行为及其流变行为和导电性能。Brij 30、Triton X-100、Brij 97和NP-10等非离子表面活性剂均能在水中形成溶致液晶,但只有Brij 97在硝酸乙基铵(EAN)中形成了溶致液晶。对此液晶体系使用变温小角X射线散射(SAXS)、变温偏光显微镜(POM)和差示扫描量热法(DSC)等技术进行了T-X相图测定和结构分析。SAXS结果表明具有双折射性的样品散射峰对应的散射因子的比例符合1：(?)3：(?)4：(?)7的关系,结合POM可确定本体系主要形成了六角相(H1)溶致液晶。根据SAXS峰的个数和强弱可以得出,体系具有较好的有序性,并呈现从液晶区的中间区域向边界区域降低的特点。对其结构参数的计算表明,随着离子液体浓度的减小,六角堆积中柱间距离逐渐减小。进一步分析得出Brij 97分子构建液晶时不是完全伸展的,而是以一定的弯曲度在液晶相中排列。EAN主要分散在PEO嵌段之间,并且形成了N-H…O(CH2)2、N-H…O-NO2、N-H…N-H、N-H…O-H、O-H…O-NO2和O-H…O(CH2)2等类型的氢键网络,促进了溶致液晶的形成。温度的升高则可减弱PEO和EAN之间的氢键,增强分子运动,导致柱状有序聚集结构的破坏,并逐渐消失。比较Brij 97在各种溶剂中的聚集行为得出,从H20到EAN到[Bmim][PF6]、[Bmim][BF4].[Pyrr][NO3]和EAB,Brij97在其中构建有序分子聚集体的能力逐渐减弱,与溶剂Gordon参数的变化一致,同时从溶剂驱动力和形成氢键网络的能力等方面进行了分析。样品倒置不流动,黏度曲线显示它们在零剪切下具有较高的表观黏度,随着剪切速率升高而产生剪切变稀行为。黏弹性分析表明低浓度时此体系存在相交频率。在相交频率之前,损耗模量(G")大于储能模量(G’),样品呈现粘性行为为主；大于相交频率,G’大于G”,样品的弹性占主导。在表面活性剂浓度较高时,相交频率消失,在整个频率范围内G’>G"。储能模量(G’)随着表面活性剂浓度的逐渐增加开始相对稳定,在临近液晶与各向同性溶液的边界时迅速降低,说明黏弹性能在液晶相区的中间区域较好,而在临近边界区稳定性较差。电导率测试分析表明此体系即使在高黏度的液晶区仍具有较好的导电性,较Brij 97/H2O体系有很大的提高。第三部分主要通过变温SAXS、变温POM和流变性能测试分析等技术研究了三嵌段共聚物Pluronic P123(EO2oP07oEO20)在质子化离子液体硝酸吡咯烷盐([Pyrr][NO3])中的聚集行为、相转变、影响因素及其黏弹性等流变性能,结果表明体系为相态转变、分子聚集和结构变化呈现一定的规律性,具有很好的黏弹性的溶致液晶型凝胶。首先,绘制了此二元体系的相图,结果显示P123/[Pyrr][NO3]体系可以在很宽的浓度范围内形成溶致液晶。通过POM和SAXS结果分析,可确认此体系主要形成了六角相、层状相及两相共存的溶致液晶。对六角相溶致液晶的结构分析表明随着浓度增加晶格间距逐渐减小,说明表面活性剂分子在有序分子聚集体中的排列更加紧密。层状相溶致液晶在此方面表现出相似的变化规律。因而,在整个液晶区范围内,随着浓度的升高,零剪切速率下的表观黏度由30%浓度下的18 PaS、75%下的676 PaS到样品总浓度为95%的5530 PaS,有较大的提高。变温研究发现,温度对溶致液晶的结构有较大的影响。对于六角相,温度升高,有序性先趋于稳定,而后逐渐降低,晶格参数逐渐增大；对于混合相,温度升高,逐渐变为层状相结构；在层状相区,温度升高,有序性先是逐渐升高或变化很小,然后逐渐降低,层间距有所增大,但较六角相更为稳定。而高浓度的样品受温度影响较大,如95%的样品,略微升温,层状相即消失。变温POM的观测结果同SAXS结果基本一致。黏度曲线表明此系列样品表现出剪切变稀的行为,而在各相区中,一般浓度越大,样品的结构越稳定,越不易剪切变稀。对其进一步黏弹性能表征分析得出除了各相区较低浓度的样品外,大多数样品表现出G’大于G",复合黏度随着角频率线性降低,结合其模量、黏度值的大小及变化规律可得出此体系为具有较好黏弹性的溶致液晶型凝胶。第四部分主要合成了一系列长链毗咯烷类和长链吗啉类氮杂环离子化合物,使用N-甲基咪唑和毗咯烷与不同链长的脂肪酸构建了非共价双亲分子,并通过核磁共振(1H NMR)和质谱(MS)等技术对其结构进行了表征。使用DSC、TGA、POM和SAXS等手段探索分析了它们的热性能、相转变及其在水溶液中的聚集行为和结构特征,进一步对其聚集形成的溶致液晶等有序分子聚集体进行了结构表征与分析。首先,对一系列不同链长的质子化吡咯烷溴化物的热重分析表明此类化合物在250℃之前具有较好的热稳定性,而且受链长的影响较小。DSC和POM结果确认了热转变过程中T相热致液晶的形成。形成T相所需要的温度随着化合物链长的增加而升高。通过电导率法测试分析此类化合物的临界胶柬浓度(CMC)表明,其值随着表面活性剂链长的增加逐渐降低。进一步升高浓度可形成六角相溶致液晶,但稳定性较差,在放置过程中逐渐转变为有序的丝线状结构,形成此结构的原因可能是表面活性剂沿六角状液晶轴向生长、堆积与定向排列。其次,合成了具有不同链长的六元氮杂环长链吗啉盐类的化合物,其热稳定性相对以上吡咯烷盐类较差,可归因于此六元氮杂环中氧原子的影响。DSC结果表明,其在熔化之前已开始分解,并出现了多个相转变。进一步对具有较大阴离子体积的[Mor1,12]BF4分析表明,其熔点相对于同链长溴盐大大降低,在87.6℃就熔化成为各向同性液体,通过变温POM确认出现了SmA相。其热稳定性也提高很多,达400℃。由此可见阴离子对此类化合物的相转变和热性能影响很大。电导率法分析此类化合物在水中的CMC得出,其值随着链长增加逐渐降低,并相对于同链长的吡咯烷类化合物有所升高。然后,使用N-甲基咪唑分别与不同链长的脂肪酸构建了双亲分子,并通过POM和SAXS等技术研究了它们在水中的聚集行为。结果表明,此体系可以在很宽的浓度范围内形成层状相,液晶体系中水的增加与分布遵循典型的一维溶胀机理。链长较短的癸酸与甲基咪唑构建的双亲分子也可形成有序性很好的层状相。两体系较易形成层状相的原因是疏水作用、氢键网络结构和π-π互作用综合的结果。最后,使用吡咯烷与月桂酸、肉豆蔻酸和棕榈酸等构建双亲分子,并研究了其在水中的聚集行为。三种体系均可在很宽的浓度范围内形成层状相。SAXS等结果表明,链长和浓度对结构参数影响较大。同浓度时,链长越长,层间距越大；同体系,浓度越大,层间距越小。肉豆蔻酸和棕榈酸构成的液晶体系,在SAXS曲线上出现两套层状相散射峰,可归因于具有较长链长的羧酸形成的复合物在高浓度时受到破坏,出现了两种比例的双亲分子,分别在水中形成不同结构的层状相溶致液晶所致。更多还原

【Abstract】 Ordered molecular assemblies, such as micelles,vesicles,lyotropic liquid crystal (LLC),and microemulsion,fabricated by amphiphilic molecules in suitable solvents are playing active roles in areas of materials,life, pharmaceutical, separation, dispersion, information,and energy. In respect of the self-assembly media, self-assemblies formed in traditional media such as water and various organic solvents might be limited in application because the system generally has poor stability, volatility, low conductivity and other shortcomings.Ionic liquids have special physical and chemical properties such as low volatility, wide electrochemical window, non-flammability, good thermal stability, etc.They are regarded as environmentally benign solvents and their application in molecular assemblies is of great interest. Recently, the development of protic ionic liquids (PILs),which can be used to build up a hydrogen-bonded network with the presence of proton-donor and-acceptor sites and easily purified, protic,is growing.The filed of self-assembly in PILs is especially active,which develop the self-assembly media and is useful when water is undesirable or proton is needed such as in the filed of proton conducting electrolyte in fuel cells, life, biocatalysis,and so on.On the aspect of amphiphiles, imidazolium amphiphilic compounds with long chain derivated from imidazolium ionic liquids have been widely used to construct micelles, microemulsions, lyotropic liquid crystal and gel ordered molecular aggregates,and further applied in the material preparation,and so on.In recent years,studies have shown that other long-chain heterocyclic compounds can exhibit excellent performance, and its application in fabricating ordered molecular aggregate has been paid attention, which can develop novel molecular aggregate system and provide potential applications.This dissertation is focused on the use of protic ionic liquids and nitrogenous heterocyclic compounds in ordered molecular assemblies.The main purpose is to construct novel LLC systems with protic ionic liquids as solvents and investigate their structure and properties, to synthesis and characterize nitrogenous heterocyclic compounds and investigate their properties and applications in ordered molecular assemblies.The outline and contents of this dissertation are as follows:In the first section,the research background of this work including the history and recent progress of surfactants and ionic liquids is summarized.The protic ionic liquids, nitrogenous heterocyclic compounds and their application in ordered molecular assemblies are briefly introduced.The research ideas, content, and significance of this dissertation are also pointed out at the end of this part.In the second section,aggregation behavior of Brij 97 (C18∶1EO10) in protic ionic liquids and their rheological and electric behaviors were investigated.Several polyoxyethylene amphiphiles, like Brij 97,Brij 30,Triton X-100,and NP-10,all of which can form LLC in water,,but only Brij 97 can be used to fabricate LLC in EAN. The T-X phase behavior and self-assembly behavior were characterized by several techniques such as small angle X-ray scattering (SAXS), polarized optical microscopy (POM), and differential scanning calorimetry (DSC).It is found that The scattering factor (q) values of Bragg peaks of the LLC system are correlated with the relative positions of 1:√3:2:√7, which is characteristic for a hexagonal liquid crystalline phase (H1).It could be concluded that the hexagonal LLC is self-organized well in the binary system and its ordering in the middle LLC range is better than that near the boundaries between micellar solutions based on the numbers and strength of the Bragg peaks.From the lattice spacing, it can be concluded that the Brij 97 molecules in H1 phase are not fully extended and conformational isomerization of the alkyl chains exists in the liquid crystalline phase. EAN molecules distribute mainly among PEO blocks and form network with them by H-bonding of types like N-H…O(CH2)2,N-H…O-NO2, N-H-N-H, N-H…O-H, O-H…O-NO2, and O-H…O(CH2)2.Temperature elevation mainly weakens the hydrogen bonds between PEO blocks and EAN and results in the decreasing of the cylindrical ordering, but the distance between the cylinders is less affected.To investigate the solvent effect, a degraded ability to produce the ordered self-assembly of Brij 97 from H2O to EAN to [Bmim][PF6],[Bmim][BF4],[Pyrr][NO3],and EAB is found and analyzed based on the molecular packing and Gordon parameters, and also hydrogen-bonding or solvophobic interactions.Rheological measurements show that these unflowable samples on the top of inverse tubes exhibit high apparent viscosity at low shear rate, and the shear-thinning phenomenon is observed.Rheograms of the oscillatory shear were also compared.A crossover frequency is found at lower Brij 97 concentration. Before it, the loss modulus (G")is higher than the storage modulus(G’) showing a viscous behavior, and at higher frequencies,G’ becomes larger than G" where the elastic response dominates.At higher Brij 97 concentrations, the crossover frequency disappears and G’>G" exists in all the frequency range.This system also shows good conductivity compare with that in water.In the third section,the aggregation behavior, phase transformation,effect factors, and rheological behavior of triblock copolymer Pluronic P123 (EO20PO70EO20) in a protic ionic liquid,pyrrolidinium nitrate([Pyrr][NO3])have been investigated by the techniques of SAXS,POM, and rheological measurements.It is found that the samples are highly viscoelastic LLC gels.Firstly, the phase diagram of this binary system was constructed,P123 can form hexagonal and lamellar LLC in [Pyrr][NO3] in a wide concentration.Structural analysis of hexagonal LLC shows that the lattice spacing gradually decreased with the increased concentration and the ordered aggregates arranged more closely. Lamellar LLC has similar properties.Temperature effect is also investigated for the system.The results indicate that the ordering gradually reduced and the lattice parameter increased with the increased temperature for the hexagonal phase.The mixed phase has the trend to become lamellar LLC when the temperature is increased.For the lamellar LLC,the ordering changes a little at first and then reduced, and the lattice parameter increased with the increased temperature.Compare to the hexagonal phase,lamellar phase is more stable.But for the samples with high concentration like 95%, the LLC is easily destroyed by increased temperature.Rheological measurements show that these samples show high apparent viscosity at low shear rate,and it’s increased with concentration.The shear-thinning phenomenon is also observed.In each phase region,the higher the concentration,the more stable the structure of the sample, and it’s more difficult to shear thinning.Further characterization of their viscoelastic properties shows that most samples are G’>G" except the samples at low concentration in ecah phase region, and the complex viscosity has a linear decrease.These results indicate that most of the samples of the system are LLC gels with highly viscoelastic properties.In the fourth section,a series of protic tertiary pyrrolidinium surfactants, morpholinium compounds with long chain, amphiphilic molecules composed of N-methylimidazole or pyrrolidine with different fatty acids were prepared and characterized by several techniques such as 1H NMR and MS.Their thermal behaviour, phase transition,and self-assembly in water were further investigated by DSC,TGA,POM, and SAXS.The LLC behavior were analyzed in detail.Firstly, the protic pyrrolidinium surfactants have good thermal stability before 250℃and were less affected by chain length.DSC results show that T phase appeared during the thermal transition, which has also been further confirmed by POM. The longer chain length the compounds have, the higher temperature required for the formation of T phase.Through the conductivity of them in water, it can be concluded that their CMC decrease with chain length increased. Hexagonal LLC can be formed by further increase of concentration, but their stability is poor, and the longer the chain is, the more difficult it is to form LLC.Ordered linear structure was formed during holding. The reasons for the formation of this structure may be the growth, accumulation, and alignment of surfactants along the column of hexagonal LLC.Secondly, Six-membered morpholinium compounds with different chain length were systhesized and characterized.Their thermal stability is worse than that of similar pyrrolidinium compounds, which may be due to the oxygen atom of the morpholinium heterocycle. DSC results show that they are decomposed before melting and T phase was formed in the process.When lager anion were introduced in the compounds like [Mor1,12]BF4, its melting point could be reduced markedly below 100℃, and SmA phase could be formed in the heating process.Its thermal stability is also greatly increased,and it is not decomposed until 400℃.Therefore,anions play an important role for its phase transformation and performance.It is also found that the CMC of these compounds decreased with the increasing chain length, and it increased a little compare to that of similar five-membered pyrrolidinium compounds.Thirdly, amphiphile was constructed by N-methylimidazole with different fatty acids, and their aqueous aggregation behavior was further investigated by POM,SAXS techinques.It is concluded that this novel ternary system can exhibit La phase with its lamellar spacing changing regularly in a wide concentration range.The relationship between uptake of water and the lattice spacing reflects a typical one-dimensional swelling. The amphiphile fabricated by decanoic acid with a shorter carbon chain and N-methylimidazole also can form well ordered La phase.Three driving forces, hydrophobic interaction, H-bonding interaction,andπ-π. interactions can be considered to be mainly responsible for such an ordered assembly. Finally, the phase behaviour of non-covalent amphiphile constructed by pyrrolidine with lauric acid, myristic acid and palmitic acid in water was investigated.The results showed that all the three systems can form ordered lamellar phase in a wide concentration range.It is found that chain length and concentration play an important role on the structural parameters by SAXS analysis.The longer the chain length, the greater the spacing parameters at the same concentration.The greater the concentration, the smaller the layer spacing in the same system.For the system including myristic acid and palmitic acid, there are two sets of peaks for lamellar structure.This can be attributed to the formation of La phase with different structure by two kinds of amphiphiles, which is formed because of the partly decomposed complex with carboxylic acids having a longer chain length in higher concentration.Thanks for the supports from the National Natural Science Foundation of China (No.20573066,20773080 and 20973104).更多还原