pH- and Redox-Responsive Pickering Emulsions Based on Cellulose Nanocrystal Surfactants

Nanoparticle surfactants (NPSs), formed by using dynamic interactions between nanoparticles and complementary ligands at the liquid-liquid interface, have emerged as “smart emulsifiers” with attributes of high emulsification efficiency, long-term stability, and on-demand emulsification/demulsification capabilities. However, only pH-responsiveness can be adopted for the assembly of reported NPSs formed by electrostatic interactions. Here, we propose an alternative design strategy, by taking advantage of the ferrocenium (Fc⁺) sulfate ion pair, to develop a new type of cellulose nanocrystal (CNC) surfactant. The Fc⁺ groups are sensitive to pH, redox reagents and voltage, imparting the CNC surfactants and derived Pickering emulsions with multi-stimuli-responsiveness, and showing promising applications in controllable delivery, release, and biphasic biocatalysis.     

Pickering乳状液的研究进展

随着纳米技术的发展以及Pickering乳液在食品、化妆品、医药等领域的潜在应用前景,人们对Pickering乳液给予了关注。本文全面总结了近些年来Pickering乳液的研究进展,对本课题组在Pickering乳液研究领域所取得的成果进行了介绍。本文主要分为4个部分:第一部分概述了Pickering乳液的研究现状;第二部分全面考察了Pickering乳液的各种影响因素;第三部分介绍了Pickering乳液的转相特性;最后综述了颗粒和表面活性物质协同稳定乳液的研究进展。这些研究成果促进了乳液基础理论的发展,并且拓展了乳液的应用范围。     

High‐Internal‐Phase Pickering Emulsions Stabilized Solely by Peanut‐Protein‐Isolate Microgel Particles with Multiple Potential Applications

High‐internal‐phase Pickering emulsions have various applications in materials science. However, the biocompatibility and biodegradability of inorganic or synthetic stabilizers limit their applications. Herein, we describe high‐internal‐phase Pickering emulsions with 87 % edible oil or 88 % n‐hexane in water stabilized by peanut‐protein‐isolate microgel particles. These dispersed phase fractions are the highest in all known food‐grade Pickering emulsions. The protein‐based microgel particles are in different aggregate states depending on the pH value. The emulsions can be utilized for multiple potential applications simply by changing the internal‐phase composition. A substitute for partially hydrogenated vegetable oils is obtained when the internal phase is an edible oil. If the internal phase is n‐hexane, the emulsion can be used as a template to produce porous materials, which are advantageous for tissue engineering.     

光交联Pickering乳液中的粒子稳定剂制备胶体体微胶囊

研究了光敏性聚合物刷修饰二氧化硅纳米粒子的制备及其乳化行为, 提供了一种制备新颖“胶体体”微胶囊的方法. 首先, 在二氧化硅纳米粒子表面引入原子转移自由基聚合(ATRP)引发剂分子, 通过表面引发ATRP得到含有香豆素侧基聚合物刷光敏性的纳米二氧化硅粒子(SiO₂-PMMA-PCMA); 然后, 以该粒子为乳化剂制备油包水型的皮克林乳液; 最后, 在紫外光的照射下引发香豆素侧基的交联反应从而得到“胶体体”微胶囊. 结果表明, 香豆素单体7-(2-甲基丙烯酰乙氧基)-4-甲基香豆素(CMA)和SiO₂-PMMA-PCMA在紫外光作用下都可以发生交联反应, 以SiO₂-PMMA- PCMA纳米粒子作乳化剂可以制备稳定的皮克林乳液, 光交联后得到的“胶体体”微胶囊的平均粒径约为170 μm.     

羧甲基纤维素钠修饰的聚氨酯泡沫制备磁性吸油材料

采用聚氨酯泡沫为模板,依次修饰羧甲基纤维素钠(CMC)、Fe~(3+),在惰性气氛中高温热处理反应,制备多孔结构的磁性吸油材料.用光学显微镜、扫描电子显微镜、红外吸收光谱、X-射线衍射、接触角等技术对材料进行表征.详细考察了加热反应温度、CMC浓度和Fe~(3+)浓度对材料吸油性能和磁性的影响规律.实验表明,当加热反应温度选择230°C,CMC浓度为0.3 wt%,FeCl_3浓度为0.1 mol/L时,材料吸油性能最佳,对正己烷、二甲苯、环己烷、甲苯、乙酸乙酯、氯仿、机油、原油等有机溶剂和油类分子的吸附容量为10倍左右.磁性多孔材料具有明显的亲油、疏水特性,水的接触角达115.9°,同时材料密度只有0.036g/cm~3,能够漂浮于水面,实现对水面有机溶剂的快速吸附.吸附后的材料在外界磁场控制下,能够通过磁分离方式从水面快速分离.该材料具有良好的循环利用性能,可重复使用20次以上,吸油性能仍然保持良好.     

Pickering乳液在功能高分子材料研究中的应用

功能高分子材料制备的瓶颈问题是如何解决多重材料的相容性问题,传统的物理共混技术和聚合添加技术无法保证材料的稳定性及均一性。 Pickering乳液具有成本低、毒性小、环境友好、稳定性好、制备的多重材料结构稳定等优点,在制备功能高分子材料的应用中越来越受到人们的重视。 本文详细介绍了Pickering乳液在功能性高分子材料制备中的应用研究进展,提出了Pickering乳液聚合制备功能高分子材料面临的一些问题,并结合本课题组的研究方向,对其发展前景进行了展望。     

纤维素类高分子表面活性剂

纤维素类高分子表面活性剂因其具有原料丰富,可生物降解,使用安全性好等一般合成高分子表面生剂所难以具备的优点,目前正引起人们的广泛关注。本文综述了近２０年来其主要研究进展,内容涉及含长链烷基,含碳氟基团和含双亲链段３类纤维素类表面活性剂。     

Surfactant Assembly within Pickering Emulsion Droplets for Fabrication of Interior‐Structured Mesoporous Carbon Microspheres

Large‐sized carbon spheres with controllable interior architecture are highly desired, but there is no method to synthesize these materials. Here, we develop a novel method to synthesize interior‐structured mesoporous carbon microspheres (MCMs), based on the surfactant assembly within water droplet‐confined spaces. Our approach is shown to access a library of unprecedented MCMs such as hollow MCMs, multi‐chambered MCMs, bijel‐structured MCMs, multi‐cored MCMs, “solid” MCMs, and honeycombed MCMs. These novel structures, unattainable for the conventional bulk synthesis even at the same conditions, suggest an intriguing effect arising from the droplet‐confined spaces. This synthesis method and the hitherto unfound impact of the droplet‐confined spaces on the microstructural evolution open up new horizons in exploring novel materials for innovative applications.     

Synergetic Effect of Reactive Surfactants and Clay Particles on Stabilization of Nonaqueous Oil-in-Oil (o/o) Emulsions

Although surfactants and particles are often used together in stabilization of aqueous emulsions, the contribution of each species to such stabilization at the oil-water interface is poorly understood. The situation becomes more complicated if we consider the nonaqueous oil-oil interface, i.e, the stabilization of nonaqueous oil-in-oil (o/o) emulsions by solid particles and reactive surfactants which, to our knowledge, has not been studied before. We have prepared Pickering nonaqueous simple (o/o) emulsions stabilized by a combination of kaolinite particles and a nonionic polymerizable surfactant Noigen RN10 (polyoxyethylene alkylphenyl ether). Different pairs of immiscible oils were used which gave different emulsion stabilities. Using kaolinite with equal volumes of paraffin oil/formamide system gave no stable emulsions at all concentrations while the addition of Noigen RN10 enhanced the emulsion stability. In contrast, addition of Noigen RN10 surfactant to silicon oil-in-glycerin emulsions stabilized by kaolinite resulted in destabilization of the system at all concentrations. For all systems studied here, no phase inversion in simple emulsion was observed by altering the volume fraction of the dispersed phase as compared to the known water-based simple Pickering emulsions.      

Synthesis and Evaluation of Some Schiff Base Surfactants for Treating Crude Oil Emulsions

Water soluble nonionic surfactants based on Schiff base monomers were prepared by their etherification with β,^` β- dichlorodiethylether and PEG 400 in presence of NaOH. The surface properties of the prepared surfactants were determined by measuring the surface tension at different temperatures. The prepared nonionic surfactants were evaluated as demulsifiers for synthetic water in crude-oil emulsions that were pronounced at different ratios of crude oil: water at 45°C and 60°C. The experimental results showed that the dehydration rate of the prepared demulsifiers reached 90% and 100% at some concentrations.     

纤维素纳米晶体的制备及其在复合材料中的应用

纤维素纳米晶体是纤维素原料经加工而得到的纳米级棒状或球状晶体。由于其具有高强度、大比表面积、生物相容性、可再生性和可降解性等优良性能,可应用于复合材料、生物医药和环境等多个领域。本文详细综述了近年来制备纤维素纳米晶体的常用方法,包括酸水解法、氧化法、酶水解法、机械法、溶剂法以及组合法。同时,讨论了各种制备方法的优缺点。在应用研究方面,本文总结了其在增强复合材料、膜过滤复合材料、导电复合材料和无机纳米复合材料等热门领域的研究情况。最后,对纤维素纳米晶体的未来发展方向进行了展望。     

基于纤维素的气凝胶材料

纤维素是自然界中储量最为丰富的一种天然高分子。作为继无机气凝胶和合成聚合物气凝胶之后的第三代气凝胶,纤维素基气凝胶材料兼具绿色可再生的纤维素材料和多孔气凝胶材料两者的优点,成为纤维素材料研究与应用中的一个热点。本文梳理了纤维素基气凝胶材料的发展脉络,综述了纤维素基气凝胶材料的研究进展。重点对纤维素基气凝胶的制备方法进行了总结,包括基于含水溶剂和无水溶剂的纤维素直接溶解法及源自植物纤维素和细菌纤维素的纤维素纳米纤维的水相分散法。介绍了纤维素基气凝胶力学性能的提高和功能性开发的最新研究结果。最后对纤维素基气凝胶材料的发展前景和研究方向进行了展望。     

纤维素纳米晶体薄膜的制备与表征

讨论了两种新型纤维素纳米晶体(Cellulose nanocrystal,CNC)薄膜的制备方法:浸没法和旋涂法,并利用红外反射吸收光谱(Infrared reflection absorption spectroscopy,IRRAS)和原子力显微镜(Atomic force microscopy,AFM)对其进行表征。AFM高度图显示两种工艺制备的CNC薄膜均由棒状的CNC纳米颗粒交错叠加而成。实验结果显示,旋涂法制备的薄膜更加光滑,粗糙度RMS约为2.7 nm。由于带电颗粒间斥力的存在,浸没法制备的CNC膜厚度最大约为15 nm,而旋涂法可以得到更厚的CNC薄膜,其厚度可达50 nm以上。研究CNC悬浮液浓度与旋涂法CNC膜厚之间的关系后发现,可以通过改变CNC溶液的浓度对薄膜厚度进行控制。IRRAS结果也证实随着CNC悬浮液浓度的增加,旋涂薄膜的厚度随之增加。     

Pickering emulsions: Versatility of colloidal particles and recent applications

The versatility of colloidal particles endows the particle stabilized or Pickering emulsions with unique features and can potentially enable the fabrication of a wide variety of derived materials. We review the evolution and breakthroughs in the research on the use of colloidal particles for the stabilization of Pickering emulsions in recent years for the particle categories of inorganic particles, polymer-based particles, and food-grade particles. Moreover, based on the latest works, several emulsions stabilized by the featured particles and their derived functional materials, including enzyme immobilized emulsifiers for interfacial catalysis, 2D colloidal materials stabilized emulsions as templates for porous materials, and Pickering emulsions as adjuvant formulations, are also summarized. Finally, we point out the gaps in the current research on the applications of Pickering emulsions and suggest future directions for the design of particulate stabilizers and preparation methods for Pickering emulsions and their derived materials.     

多孔材料的胶囊化储氢

氢的存储是氢能利用的关键,利用多孔材料的胶囊化作用存储氢气具有独特优点。本文简要阐述了胶囊化形成的原因,重点介绍了胶囊化储氢所用的几种多孔材料及其特点,包括沸石分子筛、金属配位化合物、玻璃微球和球碳及其衍生物。总结了近年来国内外学者利用多孔材料胶囊化作用储氢的研究进展,并从操作条件、对材料的要求、需要克服的能垒等方面分析了胶囊化储氢与物理吸附储氢的差异,进而对今后胶囊化储氢的应用与发展做出了展望。     

Enhancing Removal of Cr(VI), Pb2+, and Cu2+ from Aqueous Solutions Using Amino-Functionalized Cellulose Nanocrystal

In this work, the amino-functionalized cellulose nanocrystal (ACNC) was prepared using a green route and applied as a biosorbent for adsorption of Cr(VI), Pb²⁺, and Cu²⁺ from aqueous solutions. CNC was firstly oxidized by sodium periodate to yield the dialdehyde nanocellulose (DACNC). Then, DACNC reacted with diethylenetriamine (DETA) to obtain amino-functionalized nanocellulose (ACNC) through a Schiff base reaction. The properties of DACNC and ACNC were characterized by using elemental analysis, Fourier transform infrared spectroscopy (FT-IR), Kaiser test, atomic force microscopy (AFM), X-ray diffraction (XRD), and zeta potential measurement. The presence of free amino groups was evidenced by the FT-IR results and Kaiser test. ACNCs exhibited an amphoteric nature with isoelectric points between pH 8 and 9. After the chemical modification, the cellulose I polymorph of nanocellulose remained, while the crystallinity decreased. The adsorption behavior of ACNC was investigated for the removal of Cr(VI), Pb²⁺, and Cu²⁺ in aqueous solutions. The maximum adsorption capacities were obtained at pH 2 for Cr(VI) and pH 6 for Cu²⁺ and Pb²⁺, respectively. The adsorption all followed pseudo second-order kinetics and Sips adsorption isotherms. The estimated adsorption capacities for Cr(VI), Pb²⁺, and Cu²⁺ were 70.503, 54.115, and 49.600 mg/g, respectively.     

羧甲基纤维素系列高分子表面活性剂形成微乳液的研究

采用紫外光谱、相图、动态激光光散射、同位素示踪、光学显微镜、电导率等研究了羧甲基纤维素系列高分子表面活性剂与甲苯-水-异丙醇体系微乳液的形成过程,发现微乳液粒子大小均一,形态一致,其尺寸比低分子表面活性剂所形成的微乳液粒子大得多.醇分子插入到油水界面,改变了两相界面结构,促使微乳液的生成.电导率测定表明所形成的微乳液区均为水包油结构,即使在富含甲苯区域,亦不会有油包水的反相胶束形成.     

一步碳化多孔有机材料制备多孔碳及其性能的研究

开发并利用清洁的、可再生的能源是解决环境污染问题和能源短缺的有效方法.碳化含碳量较高的多孔有机材料制备的多孔碳,具有较高的比表面积,良好的物化稳定性,优良的机械性能等优点,在清洁能源的存储、分离、能量的存储与转化领域有广泛的应用.常见的由多孔有机材料制备多孔碳的方法主要是非活化碳化法和活化碳化法.不同的制备方法得到的多孔碳形貌,孔结构各不形同.多孔碳材料自身的结构性质可以影响其应用.合理的设计并调控多孔碳的“孔”,发挥孔尺寸的“筛分效应”可以有效地对气体进行存储和分离.在锂电等能量转化领域,“限域效应”是影响锂电性能的重要因素.多孔碳材料中较小的孔可以限域活性成分,而较大的孔可以快速传输,两种孔的协同效应可以使锂电性能大大提升.本综述系统地归纳了一步碳化多孔有机材料制备多孔碳的方法及其优势,详细地介绍了其在气体吸附、存储、分离以及电化学等领域的应用.最后,结合多孔碳材料的研究现状,提出由多孔有机材料制备多孔碳材料所面临的挑战,同时也展望了多孔碳材料的应用前景.