离子液体表面活性剂在水溶液中的自组装及其调控研究进展

离子液体表面活性剂在化学合成、材料制备和环境污染控制等方面的应用与它们在水溶液中的自组装及其微观结构密切相关。因此,研究离子液体表面活性剂在水溶液中的自组装行为具有重要的意义。本文重点综述了阳离子的结构、阴离子的类型、外加电解质、有机添加剂、环境因素(温度、溶液pH值和光)等对离子液体表面活性剂在水中的自组装行为以及对组装体结构影响的研究进展,总结了这些因素对离子液体表面活性剂在水中自组装的调控规律,展望了该领域的发展方向及面临的挑战。     

表面活性剂在溶液中聚集形态的动力学模拟

用耗散颗粒动力学模拟方法(DPD)展示了表面活性剂分子在溶液中的聚集形态，用扩散程度表征了表面活性剂溶液中的自组装情况。结果发现：这种分子动力学模拟方法能够直观地得到表面活性剂的聚集形态；随着表面活性剂的浓度增加，聚集形态依次从球状胶束、棒状或虫状胶束，六角状相，向层状相变化。     

疏水缔合聚丙烯酰胺与双子表面活性剂的相互作用

制备了一种脂肪酸酯双磺酸盐型双子表面活性剂, 利用粘度法、界面张力法和原子力显微镜研究了疏水缔合聚丙烯酰胺与双子表面活性剂在溶液中的相互作用. 实验结果表明: 疏水缔合聚丙烯酰胺在溶液中能够通过自组装形成疏水微区并发展成网络结构, 疏水微区与表面活性剂在溶液中能形成混合胶束; 当一定量的表面活性剂加入时, 对疏水缔合聚丙烯酰胺的自组装起促进作用, 而过多双子表面活性剂的加入又会对聚合物分子的自组装起抑制作用, 从而显著影响疏水缔合聚丙烯酰胺的溶液性质, 随着表面活性剂浓度的增加, 聚合物溶液粘度先增加、再降低; 同时, 疏水缔合聚丙烯酰胺对双子表面活性剂的界面性能也有较大影响, 聚合物的加入使双子表面活性剂降低油/水界面张力的能力下降, 油/水界面张力达到平衡所需时间延长.     

拥挤环境中表面活性剂胶束化过程的低场核磁共振研究

利用长弛豫低场核磁共振(LF-NMR)方法研究了由聚乙二醇(PEG)构建的拥挤溶液环境中表面活性剂的聚集行为。通过Carr-Purcell-Meiboom-Gill(CPMG)脉冲序列所得的回波数据及反演拟合数据对不同的表面活性剂-PEG体系进行分析,结果发现:不同分子量和不同浓度的PEG溶液可用低场核磁共振方法进行区分;高浓度的PEG溶液中均能监测到胶束形成过程,而较低浓度的PEG溶液不利于其胶束化过程监测;NaCl对含有离子型表面活性剂体系的影响较为明显,而对含有非离子型表面活性剂的体系几乎无影响。该研究丰富了低场核磁共振弛豫技术在表面活性剂胶束表征过程中的应用,同时对理解生物体系中分子的自组装及功能也具有重要意义。     

刺激响应型肽自组装及其应用

肽自组装体由于具有结构稳定、易调控、生物相容性好、可生物降解等优点,在构筑新型材料及生物医药领域表现出了巨大潜力。本文介绍了肽自组装的概念、机理和应用,详细归纳了刺激响应型肽自组装的研究进展;按照刺激源的不同将刺激响应型肽自组装分为pH响应型肽自组装、温度响应型肽自组装、溶剂响应型肽自组装、光响应型肽自组装、超声波响应型肽自组装以及离子响应型肽自组装;列举了肽自组装在药物控释、脊髓损伤修复、仿酶催化、生物模板等领域的应用。最后,基于目前肽自组装存在的一些问题(如影响肽自组装结构的外界因素不易精准把控、自组装的研究与生命科学领域的交叉程度低等)对肽自组装的发展做了展望。     

环境响应性嵌段共聚物的合成、自组装及应用研究进展

近年来具有环境响应性的嵌段共聚物的研发受到了人们的广泛关注。该类型共聚物可以对外界环境刺激产生相应的结构、物理及化学性能的变化。根据外界环境刺激响应机理及类型的不同,可将其分为单一因素、双重因素以及三重因素刺激响应性嵌段共聚物三大类。针对每一类体系,本文重点综述了嵌段共聚物的设计合成、自组装以及应用等研究现状,并概括总结了各种有序聚集体(如胶束、囊泡等)随外界环境刺激(如pH、温度、光、CO_2、氧化还原剂等)所作出的响应性变化。最后,对智能型嵌段共聚物在药物控释、纳米容器制备、生物功能材料等方面潜在的应用价值和今后可能的发展方向进行了展望。     

酸碱度对金纳米结构形貌的调控及其机理研究

本文通过调节环境pH酸碱度改变聚电解质膜中氨基基团的键合状态,以控制聚电解质膜表面金纳米粒子的原位还原与自组装过程中的聚集行为,发现当聚电解质膜经pH为5.40的去离子水处理后可在其表面制备出片状金纳米结构;经pH为0.65的强酸溶液处理后,可在膜表面制备出树枝状的金纳米结构,且尺寸比pH为5.40条件下增大一倍;经pH为12.77的强碱溶液处理后,金纳米粒子的聚集状态发生改变,形成了球形纳米结构;对金纳米粒子形貌的调控机理进行了初步探讨.     

刺激响应型功能聚合物的合成及应用

刺激响应型聚合物是一类功能性聚合物,它在药物控制释放、基因载体、纳米粒子以及纳米反应器等众多领域具有广阔的应用前景,因此引起了越来越多科学工作者的关注。刺激响应型聚合物多为双亲性聚合物,可通过自组装的方式得到形态各异的聚集体,如胶束、囊泡等。在受到某些外界环境刺激时,它们会产生特异性响应,尤其是功能性聚合物嵌段会发生相应的变化,从而引起整个聚合物结构的相转变和体积相转变。根据环境刺激种类的不同,刺激响应型聚合物可以分成不同类型,本文主要介绍了pH、温度、光、分子、电化学和手性等响应型聚合物,并概括了它们的结构特点以及不同的合成方法,简单说明了它们具有刺激响应功能的作用机理,阐述了结构与性能的联系。另外,还介绍了它们的潜在应用,并对此类聚合物的发展前景作了展望。     

巨型表面活性剂的本体自组装研究和分子拓扑结构效应

嵌段共聚物通过本体自组装可在纳米尺度上形成多样化的有序结构,并有望为下一代微纳加工技术的发展提供平台.近十年来,以具有三维刚性结构的笼簇状分子作为结构基元,研究者们发展了一类独特的两亲性巨型表面活性剂体系.本文系统总结了近年来巨型表面活性剂本体自组装方向的研究进展,并特别强调了其中广泛存在的分子拓扑结构效应.实验结果表明,巨型表面活性剂可在10 nm乃至5 nm以下的特征尺寸上形成高度有序的自组装结构.更加重要的是,通过精心设计的分子拓扑结构的变化,逐步揭示了若干种由分子拓扑结构主导的非常规自组装结构的形成机理,包括多尾链巨型表面活性剂中的非常规球状相以及多头基巨型表面活性剂中的高度不对称的层状相等.这些结果推进了对两亲性大分子本体自组装中的分子拓扑结构效应的理解,并为开发基于嵌段聚合物微纳加工技术提供了重要的实验基础.     

酸碱-氧化还原双重刺激响应型表面活性剂的合成与性能

以11-氨基十一酸为原料制备了酸碱-氧化还原双重刺激响应型表面活性剂中间体11-叔胺十一烷基羰基二茂铁(C_(11)-N-Fe);采用~1H NMR和MS等手段对产物进行了结构表征;并通过透光率、循环伏安法和紫外光谱分析等研究了其酸/碱和氧化/还原开关响应性能.研究发现,C_(11)-N-Fe的盐酸盐在水溶液中进行自组装时,可制备具有酸碱-氧化还原双重刺激响应性的泡沫,且采用2种刺激方式的消泡均可在2 min之内完成;将C_(11)-N-Fe的盐酸盐作为乳化剂用于乳化正癸烷/水体系,可以制得颗粒均匀稳定的乳状液,同时可以通过酸碱-氧化还原双重刺激可逆调控乳液的稳定与破乳.     

Hydrotropic solutions

Hydrotropes are a class of amphiphilic molecules that cannot form well organized structures, such as micelles, in water but do increase the aqueous solubility of organic molecules. Often strong synergistic effects are observed when hydrotropes are added to aqueous surfactant or polymer solutions. Recent studies regarding the effects of hydrotropes on phase behavior, aggregation, surface tension, viscosity, solubility, and microstructure formation are reviewed. Novel applications of hydrotropes as molecular probes and for controlled release of pharmaceuticals are also discussed.     

Photochemical reactions of surfactant molecules in condensed monolayer assemblies--environmental control and modification of reactivity.

An investigation of the effects of a controlled microenvironment on reactivity has been carried out by the synthesis and study in organized monolayers of surfactant molecules containing photochemically reactive chromophores. Reactions where substantial environmental effects have been observed include the cis-trans isomerization of olefins, ketone photoeliminations, ligand substitution processes, excimer and photodimer formation, and photoredox reactions. Both reactions occurring within the organized assemblies as well as interfacial phenomena have been investigated. Results obtained in these studies suggest possible extensions and applications for the development of new catalyst systems, biological models and controlled syntheses.     

芳香族小分子物质在表面活性剂溶液中的状态

阴、阳离子表面活性剂在水溶液中混合后很容易形成沉淀,因而以往在应用上将这两种表面活性剂视为配伍禁忌。但是最近几年,混合阴、阳离子表面活性剂水溶液理论性质的研究受到了一种程度的重视。研究发现,该混合体系具有与单纯的离子型表面活性剂或离子与非离子型表面活性剂混合物十分不同的性质,     

Electrocatalytic Organic-Inorganic Hybrid Films and Their Applications in Chemical Sensors and Biosensors

In this report, we will present the organic-inorganic hybrid molecular films prepared in our group and their applications in chemical sensors and biosensors.Many types of multi-layered films have been prepared in an alternatively assembled organic-inorganic and layer-by-layer manner. We will focus on the alternatively organized organic surfactant and metal-complex films and their conversion into electrocatalytically active films. Especially, we will demonstrate the preparation of bifunctional films for the detection of two different but correlated species, such as nitric oxide and oxygen, in biomedia.     

A New System of Multiple Emulsions with Lamellar Gel Phases from Vegetable Oil

Emulsions are excellent pharmaceutical vehicles used in both the pharmacy and cosmetic industries. Vegetable oils have several effects/benefits on skin and can be used in emulsions to release principal active components for cosmetic purposes. Herein, multiple W/O/W emulsions were formulated in a one-step emulsification method, and the resulting anisotropic structures were characterized by x-ray diffraction measurements. The multiple emulsions obtained were stable and maintained their anisotropic structures over 2 years. WAXS (wide-angle x-ray scattering) measurements of these emulsions suggested that the carbon chains of the surfactant around the globules are disposed in a gel network phase. Furthermore, SAXS (small-angle x-ray scattering) measurements indicated that the surfactant is organized in lamellar layers around the globules. Thus, for the first time, we demonstrated that stable lamellar gel phase multiple emulsions can be made from vegetable oils. In addition to having the advantage of being prepared in one step, these emulsions have desirable characteristics that can be used in the cosmetic industry as natural active principles with low surfactant concentration and the unique features of multiple emulsions with gel phases.     

Analytical applications of organized assemblies for on-line spectrometric determinations: present and future

An amphiphile (surfactant) spread on water can lead to the formation of different aggregates: vesicles, miscelles, emulsions or microemulsions; depending on its concentration; its molecular structure and/or the experimental conditions. Such aggregates, (a) may concentrate products, reactants or analytes and so improve the analytical sensitivity and (b) may solubilize such substances and so favorably change the analytical selectivity. Bilayer membrane vesicles for instance, apart from their wide applications in cosmetic and pharmaceutical industries, have a great analytical potential due to their ability to (i) reversibly sequester metal ions avoiding matrix interference and (ii) improve cold vapor (Hg and Cd) and hydride (As, Se, Pb) chemical generation. Micellar solutions have also found wide applications in different areas of analytical chemistry, showing their capacity to concentrate and separate a significant variety of analytes. Among the numerous micelle-based separation techniques, cloud point extraction offers an excellent enrichment factor for metal ions, allowing their quantification at microgram/litre levels. Also agitating a mixture of water, oil and one or more surfactants under controlled experimental conditions, a cloudy mixture (emulsion) or a transparent solution (microemulsion) can be formed. Adequate formulation is necessary in order to obtain a stable organized media. To fulfill this requirement, a major effort is necessary in order to shorten the gap between the current knowledge on this topic and the promising field of applications that await development. Recent publications show that self-assembly structures from highly viscous samples can be accomplished on-line with the advantages of drastically reducing the time of analysis and assuring the absolute control over the stability of the aggregate. Flow systems allow effective mixing of samples with added surfactant and provide continuous pumping of the resulting mixture to sensitive detectors for the on-line determination of different analytes in complex samples.     

Hierarchically imprinted sorbents

A double imprinting methodology was developed to synthesize novel materials with hierarchical structures. On the microporous level (1-3 A), metal ions served as template. On the mesoporous level (diameters of 25-40 A), micellar structures produced by self-assembly of surfactant molecules were used as templates. Removal of both metal ions and surfactant micelles resulted in the formation of imprints with different sizes within the silica matrix, each with a specific function. This research opens vast opportunities for the applications of ordered mesoporous materials in the area of molecular recognition such as separations, chemical sensors, and catalysts.     

Kinetics of morphological changes in surfactant systems

Equilibrium structures of surfactants have been studied in much more detail than morphological changes that can occur under non-equilibrium conditions. Recent experiments attempt to analyse pathways of such morphological transitions, in particular for micellar kinetics, solubilisation and formation/break-up of vesicles. Significant progress was made with respect to the achievable time-resolution in such structural investigations, which allows to identify intermediate structures. Understanding and control of the dynamics of surfactant systems is of fundamental importance for many applications of surfactants.     

Adsorption of cationic multicharged surfactants at liquid–gas interface

We present the review of the existing methods for describing adsorption at fluid interfaces that may be applicable for multiple charge cationic surfactant structures of various architectures—multiheaded (e.g., dicephalic) structures and multimeric surfactants (e.g., dimeric (so-called gemini), trimeric, tetrameric, etc.). We discuss the role of the prefactor the in the Gibbs adsorption equation originating from the number of charges present in the adsorbed layer and the reasons for the deviation from its thermodynamic value. We present several models of adsorption that can be used to describe surface tension isotherms and appreciate the role of prof. Peter Kralchevski in their development. Application of molecular dynamics methods combined with the approach based on the thermodynamic models of multicharged surfactant adsorption may lead to an explanation of some experimentally observed phenomena and can provide the basis for the development of novel materials designated for a variety of applications.     

Peptide Nanotubes

The self‐assembly of different classes of peptide, including cyclic peptides, amyloid peptides and surfactant‐like peptides into nanotube structures is reviewed. The modes of self‐assembly are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized.