【作者】 李秋红；

【导师】 陈晓；

【作者基本信息】 山东大学 ， 胶体与界面化学， 2011， 博士

【摘要】 通过非共价键相互作用构建的超分子有序聚集体由于在催化化学、材料制备、生命科学、信息科学以及纳米科学与技术等众多领域存在着极为重要而广泛的应用价值,长期以来一直是科研领域研究的热点。本论文以离子自组装为主要构建策略,设计和组装得到环境响应性超分子聚集体,并尝试通过环糊精包结和氧化还原对其进行调控。论文的主要研究内容包括如下三部分：1.二茂铁衍生物参与自组装超分子聚集体的调控。研究包括两个方面：二茂铁衍生物分子与二辛基琥珀酸磺酸钠盐(AOT)协同自组装囊泡的氧化还原调控；二茂铁季铵盐与脱氧胆酸钠(NaDC)协同组装超分子聚集体的调控。研究表明：(1)氧化形式的N,N-二甲基二茂铁甲铵(Fc+M)和双尾链阴离子表面活性剂AOT协同构建所得囊泡的形成和破坏可通过二茂铁的氧化还原进行可逆调控。还原剂对苯二酚的加入将引起囊泡的解离,溶液转变为乳液。接下来氧化剂硫酸铈的加入会引起囊泡的重新形成。囊泡的结构和形貌可通过透射电子显微镜(TEM)和动态光散射(DLS)进行表征,颗粒平均尺寸约120nm。氧化还原反应引起囊泡形成和破坏的机理通过循环伏安(CV)和UV-vis光谱测量所获得数据来支持。机理分析表明二茂铁氧化还原态的改变会影响FcM和AOT的非共价相互作用,从而引起聚集体的转变。同时,π-π堆积和双亲疏水缔合在此调控过程中也起到了一定作用。所获得的结果以及对体系的进一步研究将为设计不含长尾链的囊泡体系的实时控制提供一定的指导。(2)利用简易的离子自组装(ISA)方法,通过复合二茂铁基三甲基碘化铵(FcMI)和NaDC所形成超分子聚集体可通过电化学氧化还原和环糊精包结进行调控。还原态FcMI和NaDC混合的水溶液通过TEM观察为无定形网状结构。将二茂铁电化学氧化后,由于亲水性的增加,超分子复合物在水体系中自组装形成高稳定性囊泡,溶剂挥发后基本保持原来的形貌而不塌陷。囊泡的形貌可通过TEM、DLS和原子力显微镜(AFM)进行详细的表征。TEM可清楚观察到囊泡结构的外壳,厚度在几到几十纳米,囊泡的直径为50-200 nm。AFM结果显示纳米球的直径和高度比约为10,表明壳的塌陷和球的空心结构。此外,考虑到二茂铁与β-环糊精(β-CD)的结合,β-CD可与Fc形成包结物,进而与NaDC作用形成的三元复合物具有类似双亲分子的结构,在水溶液中也会自组装形成囊泡。而且随放置时间增加,囊泡转变成纳米管。该研究对环境响应型超分子聚集体的制备具有一定的指导意义。2.二茂铁基三甲基碘化铵(FcMI)和双尾链阴离子表面活性剂AOT通过ISA制备蠕虫状纳米线。产物的结构和性质通过核磁共振(1H NMR)、扫描电子显微镜(SEM)、偏光显微镜(POM)、小角X射线散射(SAXS)、TEM、UV-vis.CV等表征手段进行研究。复合物中AOT和Fc的化学计量比确认为1：1。FcM-AOT复合物具有反六角柱状相结构,层间距D为2.49nm,其中Fc分子位于中心核,AOT分子环绕周围。有趣的是,这些蠕虫状纳米线交互交叉形成网状,当达到足够大之后会显示出高度有序的晶体结构。而且由于二茂铁的引入,聚集体显示出良好的氧化还原活性。若利用该简易方法制备具有光、电、磁等性能的纳米线,则聚集产物具有构建纳米机械的潜力。鉴于β-CD对二茂铁有良好的包结能力,β-CD包结二茂铁后,再与AOT作用形成的环糊精超分子复合物在水体系中自组装可形成囊泡。囊泡的形貌和结构利用TEM和DLS进行表征。利用醋酸双氧铀作为负染色剂,在三元体系中可以观察到大量的球状囊泡,球状结构直径在30～300nm左右。DLS的实验结果给出了囊泡的平均水化半径,该结果与透射电镜一致,平均水化半径约108nm。复合物的形成和转变机理通过循环伏安、紫外光谱和核磁数据来支持。该过程受到包结平衡和多种弱相互作用(静电相互作用、π-π堆积、双亲分子疏水缔结)的协同影响。此外,由于二茂铁具有还原态疏水而氧化态亲水的性质,通过电化学氧化还原改变二茂铁的状态,可实现对二元复合物所形成聚集体的可逆调控。在氧化还原激励下,通过ISA所形成超分子聚集体可在纳米线和囊泡之间可逆转变。施加+0.7V电位将二茂铁氧化后,蠕虫状纳米线消失,TEM观察溶液中有囊泡形成,直径约为50～300 nm。DLS的实验结果给出了囊泡的平均水化半径约为110nm,与TEM结果基本一致。对溶液施加-0.1V还原电位一段时间后将导致纳米线的重新形成。因此通过电化学氧化还原实现了对超分子聚集体的可逆调控。二茂铁氧化还原态性质的不同引起超分子双亲性的改变是导致聚集体转变的主要原因。而且,由于无外加物质破坏体系,电化学方法调控的这一转变过程至少可重复三次。利用这种简便易行的超分子离子自组装策略,可以设计得到形貌和功能丰富多样的软物质,人为的设计和构建分子有序聚集结构以及智能材料的发展,将是非常有意义的研究方向。3.聚丙烯酸钠(PAAS)和二茂铁表面活性剂n-烷基(二茂铁基甲基)溴化铵(Fcn,n=8,12,16,这里,n是烷基链上碳的数目)通过ISA形成氧化还原活性的聚电解质-表面活性剂复合物(PSC)。复合物的结构和性质可通过XRD、UV-vis、热重(TG)和CV等进行确定。研究发现,PAAS-Fcn复合物显示出有序的层状介观相结构,UV-vis光谱表明二茂铁基团在其中有序排列形成H-聚集体。随表面活性剂烷基链长度的增加,复合物的有序性增加。CV测量结果显示出相对于PAAS-Fc8和PAAS-Fc12, PAAS-Fc16表现出更差的电极可逆性。本研究结果表明氧化还原活性的PAAS-Fcn复合的电化学活性可通过改变表面活性剂的链长进行调控。这为ISA制备具有有序介观相结构的氧化还原活性聚合物提供了一种简单可行的方法。更多还原

【Abstract】 The supramolecular ordered aggregates via noncovalent interactions have attracted much interest in the past century due to their promising applications in diverse fields such as catalysis, material preparation, smart devices, information science, and nanotechnology. This dissertation is focused on the design and assembly of stimuli-responsive supramolecular aggregates based on ionic self-assembly strategies, and the inclusion of cyclodextrins and redox were applied to tune the aggregates. There are three main experimental studies in this dissertation as following.1. The study of tuning supramolecular aggregates assembled by ferrocene derivatives. Based on the experimental results, two researches were attempted:redox tuning of vesicles prepared in an aqueous solution through self-assembly of ferrocene derivative molecules and sodium bis(2-ethyl-l-hexyl) sulfosuccinate (AOT); the study of tuning of supramolecular aggregates assembled by ferrocene quaternary ammonium salt and sodium deoxycholate (NaDC). Following results are obtained.(1) Vesicles prepared in an aqueous solution through self-assembly of the oxidized form of N,N-dimethylaminomethylferrocene (Fc+M) and a double-tailed anionic surfactant, aerosol AOT, can be reversibly transformed by redox reactions. Adding the hydroquinone as a reducing agent will cause the dissociation of vesicles and change the solution into emulsion. Subsequent oxidization by adding Ce(SO4)2 will regenerate vesicles. The vesicle structure and morphology are characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively and the mean particle size is about 200 nm. The mechanism of vesicle formation and disruption caused by redox reactions is discussed along with the data obtained from cyclic voltammetry (CV) and UV-vis spectroscopy measurements. The redox state changes of the ferrocenyl moiety may influence the noncovalent interactions between FcM and AOT. Meanwhile, theπ-πstacking and amphiphilic hydrophobic association are also included during such a redox modulated process. These results provide guidance for the design of surfactant and small molecular systems that permit active control of self-assembly.(2) We employ a facile ionic self-assembly (ISA) route, through the complexation between (ferrocenylmethyl)trimethylammonium iodide (FcMI) and NaDC, to fabricate the complexes, and their structure and morphology can be tuned by electrochemical redox and the inclusion of cyclodextrins. The amorphous network structure can be observed by TEM when FcMI and NaDC are mixed together, and the electr-oxidation of ferrocene will induced the formation of stable vesicles due to the increase of hydrophilicity of supramolecular complexes. The vesicle structure and morphology are characterized respectively by TEM, DLS and atomic force microscopy (AFM). Their shells can be clearly noted by TEM observation with the thickness at the range of several to several tens of nanometers and their outer diameters at the range of 50-200 nm. The formation of vesicular structures is also supported via AFM observation. The ratio of the diameter and height of the nanospheres is estimated to be ca.10, which should indicate the shell collapse. What’ s more,β-CD can include Fc blocks to form stable supramolecular inclusion complexes, which look like the amphiphiles and can assemble to vesicles. With the increase of standing time, the vesicles will be transformed into nanotubes. This finding might be important for the preparation of stimuli-responsive supramolecular aggregates2. Wormlike nanowires have been successfully prepared via the ISA route from the cationic FcMI and the anionic AOT complexes. Their properties and structures are characterized respectively by 1H NMR, SEM, POM, SAXS, UV-visible spectroscopy and cyclic voltammetry. The stoichiometry between AOT and Fc in the complexes is determined as a 1:1 molar ratio. FcM-AOT complexes exhibit an ordered hexagonal columnar structure with the lattice spacing D of 2.49 nm, which is derived from the reverse hexagonal lattice of pure AOT with Fc blocks inside. More interestingly, the wormlike nanowires interweave themselves together to form a net-like structure, and some of them are large enough to exhibit a high-order crystal structure. The formed FcM-AOT complexes show good redox activity also due to the introduction of organic metal ferrocene. circle. Such easily fabricated nanowires with special properties (photo, electric and magnetic) may be used to tailor the parts of nanomachine. Considering the inclusion ofβ-CD with Fc, such an ISA organized aggregate can be changed into vesicles by including the Fc blocks intoβ-CD to form another supramolecular complex. The supramolecular structure and morphology of the vesicles were characterized by TEM and DLS, respectively. Using the uranyl acetate as a negative staining agent, we observe the closed spherical vesicles in the systems, with their outer diameters in the range of 30-300 nm. DLS measurements are also performed to measure the average diameters of vesicles. Results obtained are consistent with the ones observed with TEM, showing an average hydrodynamic diameter of about 108 nm. The mechanism of the complex formation and transition is discussed along with the data of induced cyclic voltammetry, UV-visible spectroscopy, and 1H NMR. And the transformation process are discussed and found to be controlled by the inclusion equilibrium and the cooperative binding of noncovalent interactions, including the electrostatic interactions,π-πstacking, and amphiphilic hydrophobic association. What’ s more, controlling aggregates transformations of FcM-AOT complexes are achieved by electrochemical method due to the property change of ferrocene with different form. In response to redox stimuli, the self-assembly nanostructures of supramolecular amphiphile formed by ISA can change between nanowires and vesicles. The wormlike nanowires disappear when constant potential+0.7 V are applied, and TEM observation indicates the formation of vesicles with diameters at the range of 50-300 nm, which is consistent with the ones observed with DLS measurements (about 110 nm). The application of reduction potential-0.1 V to the mixed system will induce the reformation. Such a morphology transition exhibits a reversible modulation on aggregate structures by electrochemical method. The transformation of self-assembly aggregates induced by redox reactions were found to be brought out by drastic change in amphiphilicity of the supramolecular complexes due to the oxidation and reduction of a ferrocenyl moiety. Moreover, the construction-deconstruction process can be controlled reversibly for at least three times because of without the introducing of a third substance. Therefore, through simple ISA strategy, we could expediently acquire many unique soft materials with various structures and functions from aqueous environment, and the design and construction of stable ordered assemblies and the development of smart material will be expected as one remarkable study thought.3. Redox-active polyelectrolyte-surfactant complexes (PSC) are prepared via the ionic self-assembly of sodium polyacrylate (PAAS) and ferrocenyl surfactant, n-alkyl (ferrocenylmethyl)ammonium bromide (Fcn, n=8,12,16, where n is the carbon number of the alkyl chain), in solution. Their structures and properties are characterized respectively by XRD, TG, UV-visible spectroscopy and CV. The results show that PAAS-Fcn complex exhibited an ordered lamellar mesomorphous structure with the ferrocenyl moieties forming H-aggregation as known from the blue shift in the UV spectrum. With increasing the length of surfactant alkyl chain, the stacking order is improved. CV measurements indicate that the reversibility of the electrode process becomes worse for the PAAS-Fcl2 and PAAS-Fcl6 films than that for the PAAS-Fc8. The present results demonstrate that the electrochemical activity of the redox-active polyacrylate-ferrocenyl surfactant complex can be easily tuned by changing the surfactant tail length. Our work provides a simple and facile approach to the preparation of redox-active polymers with ordered mesomorphous structure by the ionic self-assembly.更多还原