纤维素在新型绿色溶剂离子液体中的溶解及其应用*

近年来,离子液体作为一种极具应用前景的绿色溶剂受到越来越多的关注。纤维素是自然界中含量最丰富的可再生资源,必将成为未来最重要的工业原料之一。离子液体在纤维素化学领域的应用遵循了绿色化学中开发环境友好溶剂和利用生物可再生资源为原料这两个基本原则,大大拓展了纤维素的工业应用前景,为纤维素资源的绿色应用提供了一个崭新的平台。本文对纤维素在离子液体中溶解的研究进展及其在制备再生纤维素材料、纤维素衍生物及生物乙醇等方面的应用进行了综述。纤维素大分子的降解机理及其控制途径、纤维素晶态结构变化规律及其调控途径、纤维素与固体反应试剂的均相衍生化体系的建立及提高衍生化效率的途径等基础问题仍需要进一步深入研究。     

基于海鞘纤维素的先进功能材料研究进展

海洋生物质资源十分丰富,且具有多种功能基团,开发前景可观.其中,海鞘是一类能生产纤维素的海洋动物,而且其纤维素主要以纳米纤维形式存在.本文简要介绍海鞘纤维素结构及其构建的功能材料的研究进展,全面概述海鞘纤维素纳米晶体的制备、结构和形貌、力学性能以及悬浮液的性质和液晶行为.重点介绍海鞘纤维素纳米纤维在聚合物材料增强、仿生材料设计以及功能材料构建方面的应用.深入讨论生物医用、自修复、环境敏感、导电导热、分离等功能材料的构效关系.     

非均相膜聚合物囊泡的构筑、应用及展望

聚合物囊泡是通过聚合物自组装构筑的纳米组装体,由于其独特的空腔-膜层-冠层结构,在生物医用等领域具有较好的应用前景,因此越来越受到研究者的关注.不同于传统的均相膜囊泡,非均相膜囊泡的膜层由不相容的组分构成,呈现出微相分离的特点,具有丰富的功能.本文以近年来本课题组及国内外同行在非均相膜囊泡领域的研究成果为基础,详细论述了非均相膜囊泡的膜层结构、理论构筑与设计策略,讨论了其在生物大分子包载与递送、高效抗菌、癌症诊疗与糖尿病治疗、能源存储、水处理等领域的潜在应用,并对该领域的发展方向进行了展望.     

壳聚糖及其衍生物处理工业废水的研究进展

综述了近年来壳聚糖及其衍生物在处理工业废水中的应用.壳聚糖及其衍生物可处理工业废水中的重金属离子,如Cr（Ⅵ）、Cu（Ⅱ）和Zn（Ⅱ）等;可处理含染料的工业废水,如处理直接紫B、直接绿BE以及甲基橙等染料;还可用于处理印染、造纸和含油废水.壳聚糖及其衍生物具有易分离、可生物降解,无污染等特点,是绿色的水处理剂,且我国壳聚糖资源极为丰富,探索其在工业废水处理中的应用有着重要的价值.     

微纤化纤维素的制备及应用

微纤化纤维素（MFC）是一种新型的纳米级功能材料,由于其具有生物相容性、生物可降解性、优良的力学性能、光学性能以及阻隔性能,在纳米纸、气凝胶、复合材料、造纸、医药等诸多领域具有广阔的应用前景。但MFC在制备及应用过程中还存在诸多问题,例如机械处理能耗高,无法工业化生产;MFC极性强,在非极性基质中分散不均,这些都限制了其在纳米复合材料领域的发展,因此需要通过预处理降低机械处理过程中的能耗,同时系统地对MFC与聚合物复合机理进行研究以拓宽MFC的应用领域。本文综述了MFC的制备方法及其在纳米纸、气凝胶及纳米复合材料方面的应用现状,并对MFC的未来发展方向进行了展望。     

纤维素纳米晶的空间受限自组装: 从胶体液晶到功能材料

作为最有前途的生物衍生材料之一, 纤维素纳米晶体(CNCs)具有来源广泛、 生物相容性好和可形成光子结构等优点, 在能源、 生物医学和光子材料领域具有重要的应用价值. 本文总结了CNCs的制备、 CNCs形成的胆甾型胶体液晶及CNCs衍生的光子材料的研究进展, 重点评述了CNCs在液滴和毛细管中的自组装和基于CNCs空间受限组装的功能材料研究进展, 并讨论了空间受限CNCs自组装研究面临的挑战和未来的发展方向.     

静电纺丝——从无规纳米纤维膜到取向连续长纱

静电纺丝是通过对聚合物溶液或熔体施加外电场制造纳米纤维的有效方法.电纺过程中,在静电力作用下聚合物射流快速鞭动,形成的纳米纤维无规堆砌,得到无纺布状的无规纳米纤维膜.这种纳米纤维膜具有极大的比表面积,已用于超高效过滤,在刨伤修复、组织工程、水处理等领域有广泛的应用前景.为了进一步拓展纳米纤维在纤维工业、纺织品、微制造等领域的应用,电纺纳米纤维的取向和连续长纱的制备研究受到科学家的重视,文献报道了多种纳米纤维取向方法.本文分析了纳米纤维膜无规堆砌结构的形成机理,总结了纳米纤维取向研究和连续长纱制备研究进展,特别介绍了基于静电作用分析提出的共轭电纺方法,讨论了取向纳米纤维的应用以及纳米纤维未来的研究方向.     

纳米细菌纤维素膜的表征与生物相容性研究

利用木醋杆菌静态培养法制备的由纳米纤维组成的细菌纤维素膜具有超细的三维网络结构和适当的孔隙率. 利用光镜、扫描电镜和原子力显微镜对其进行结构表征发现, 细菌纤维素膜具有极为精细的纳米网络结构, 冻干膜的孔径约为0.6~2.8 μm; 纤维素带宽度约为50~80 nm. 采用湿重与浮重结合法测定烘干膜和冻干膜的孔隙率分别约为70%和90%. 由于细菌纤维素含有大量的羟基, 故烘干膜表现出极好的透湿性. 将细菌纤维素膜分别与成纤维细胞和软骨细胞进行复合培养, 并将成纤维细胞和细菌纤维素膜的复合物进行裸鼠皮下移植实验. 结果显示, 移植的复合物很好地融入了裸鼠正常皮肤, 成纤维细胞和软骨细胞在细菌纤维素表面形成连续的细胞层, 绿色荧光蛋白表达正常. 以上结果表明, 细菌纤维素膜非常适合细胞贴附和增殖, 表现出较好的生物相容性, 有望成为新型组织工程支架材料.     

可持续高分子-纤维素新材料研究进展

21世纪"绿色"化学已成为世界各国社会经济发展中的研究与开发战略方向.纤维素是自然界中储量最丰富的天然高分子,是重要的可再生资源以及未来的主要工业原料.然而由于纤维素存在着大量的分子内以及分子间氢键,其结构致密,难以溶解或熔融进一步加工.本文简要介绍了近几年来关于直接使用物理溶剂方法(非衍生化)对纤维素材料开发利用的新进展,主要包括以下4个方面:(1)纤维素在"绿色"溶剂-碱/尿素以及离子液体体系中的溶解和再生;(2)纳米纤维素的制备以及组装;(3)木材纳米技术的开发及利用;(4)细菌纤维素基材料等,旨在推进"绿色"技术实现纤维素资源的研究开发及利用.     

水滑石及其衍生物处理水中污染物的研究进展

水滑石(LDH)由于具有记忆效应、内部结构可调性、层间阴离子可交换性等优良性质,而在水处理领域具有广阔应用前景。本文综述了水滑石及其衍生物处理水中污染物的最新研究进展。介绍了LDH处理重金属废水和有机废水,利用催化氧化性能或通过与不同材料复合处理废水。此外,还简述了LDH的规模化生产现状及存在问题,对LDH材料在水处理领域的未来发展方向进行了展望。     

Porous Polyelectrolytes: The Interplay of Charge and Pores for New Functionalities

The past decade has witnessed rapid advances in porous polyelectrolytes and there is tremendous interest in their synthesis as well as their applications in environmental, energy, biomedicine, and catalysis technologies. Research on porous polyelectrolytes is motivated by the flexible choice of functional organic groups and processing technologies as well as the synergy of the charge and pores spanning length scales from individual polyelectrolyte backbones to their nano‐/micro‐superstructures. This Review surveys recent progress in porous polyelectrolytes including membranes, particles, scaffolds, and high surface area powders/resins as well as their derivatives. The focus is the interplay between surface chemistry, Columbic interaction, and pore confinement that defines new chemistry and physics in such materials for applications in energy conversion, molecular separation, water purification, sensing/actuation, catalysis, tissue engineering, and nanomedicine.     

A Review of Cellulose and Cellulose Blends for Preparation of Bio-derived and Conventional Membranes,Nanostructured Thin Films,and Composites

Cellulose has been used as a raw material for the manufacture of membranes and fibers for many years. This review gives the background of the most recent methods of treating or dissolving cellulose, and its derivatives to form polymer films or membranes for a variety of applications. Indeed, some potential applications of bacterial cellulose, nanofibrillar cellulose (NFC) for films showing enhanced barrier characteristics are reviewed as well as the utilization of cellulose nanonocrystals (CNC) for production of highly oriented super strong films or thin films is discussed. Because of the success of the Lyocell process as well as the amine/metal thiocyanate solvent blends of cellulose and other polysaccharides like starch, chitosan, and other natural polymers. Consequently, the use of cellulose (or its derivatives) and another polysaccharide dissolved as a blend is also elaborated. It is our hope that the reader will want to follow up and investigate these new systems and use them to develop end use materials for all sorts of applications, from medical to water filtration, or electrogels for use in batteries.     

Microfibrillated cellulose and new nanocomposite materials: a review

Due to their abundance, high strength and stiffness, low weight and biodegradability, nano-scale cellulose fiber materials (e.g., microfibrillated cellulose and bacterial cellulose) serve as promising candidates for bio-nanocomposite production. Such new high-value materials are the subject of continuing research and are commercially interesting in terms of new products from the pulp and paper industry and the agricultural sector. Cellulose nanofibers can be extracted from various plant sources and, although the mechanical separation of plant fibers into smaller elementary constituents has typically required high energy input, chemical and/or enzymatic fiber pre-treatments have been developed to overcome this problem. A challenge associated with using nanocellulose in composites is the lack of compatibility with hydrophobic polymers and various chemical modification methods have been explored in order to address this hurdle. This review summarizes progress in nanocellulose preparation with a particular focus on microfibrillated cellulose and also discusses recent developments in bio-nanocomposite fabrication based on nanocellulose.     

Nanocelluloses: a new family of nature-based materials

Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species, such as water, organic and polymeric compounds, nanoparticles, and living cells. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the preparation of nanocrystalline cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.     

Substrate role in coating of microfibrillated cellulose suspensions

Interest in nanocellulose-based coatings for packaging applications has been growing due to their excellent oil and gas barrier properties combined with their sustainable, recyclable, biodegradable, and non-toxic nature. Coating of nanocellulose materials such as microfibrillated cellulose (MFC) on paper/paperboard is challenging compared to traditional paper coating materials due to excessively high viscosity and yield stress of MFC suspensions at rather low solids content, typically below 5%. Possessing large amounts of water and a distinct rheological behavior such suspensions set tough demands on the substrate to be coated. It is important to understand and quantify substrate requirements in order to coat these suspensions successfully and achieve a satisfactory coating quality. A custom-built slot geometry is used herein to enable coating of highly viscous MFC suspensions on different paper-based substrates in a roll-to-roll process. The impact of substrate properties, such as surface chemistry and surface energy, surface roughness and surface porosity, and water absorption capacity on MFC coatability and coating quality is reported. Coating adhesion to the substrate was quantified with surface strength testing of MFC coated substrates. Various techniques, such as Scanning Electron Microscopy, IGT print penetration tests, and air permeability tests were employed for measuring coating coverage and surface porosity. MFC coating was found to adhere best to a highly hydrophilic surface, whereas the most uniform and defect-free film at low coat weights was formed on a smooth surface. It was also found that the MFC coat weight needed for full coverage, and therefore potentially good barrier, needs to exceed the surface roughness volume of the substrate. Water absorption capacity of the substrate also determines the final MFC coating quality obtained. The results clearly highlight the role of paper-based substrate for successful and effective coating of the micro and nanocellulose suspension.     

纳米纤维素的制备*

在纳米尺寸范围操控纤维素分子及其超分子聚集体,结构设计并组装出稳定的多重花样,由此创制出具有优异功能的新纳米精细化工品、新纳米材料,是纤维素科学的前沿领域和热点。为了研究当前制备纳米纤维素的现状和发展方向,简述了纳米纤维素化学基础,介绍了三类纳米纤维素：纳米纤维素晶体（晶须）、纳米纤维素复合物和纳米纤维素纤维,重点综述了纳米纤维素的五种制备方法：化学法制备纳米纤维素晶体和晶须、生物法制备细菌纤维素、物理法制备微纤化纳米纤维素、人工合成纳米纤维素和静电纺丝制备纤维素纤维,讨论了各种制备方法的优点和缺点,指出开展纳米纤维素超分子的可控结构设计、立体与位向选择性控制与制备、分子识别与位点识别等自组装过程机理、多尺度结构效应的形成机理等基础理论性研究是主要研究基础,新型的、绿色、低能耗、快速、高效的制备方法是纳米纤维素制备方法的发展方向。     

Materials chemistry and the futurist eco-friendly applications of nanocellulose: Status and prospect

Cellulose, a linear biopolymer, is present naturally in all plants. Apart from being the planet’s predominant natural polymer, it also offers a variety of features including excellent biocompatibility, lower density, substantial strength and the most beneficial mechanical characteristics, inexpensive in cost. Applying the mechanical or chemical techniques, cellulosic materials are transformed into cellulose nanofibres (CNFs) and even cellulose nanocrystals (CNCs). These CNFs and CNCs exhibit excellent capabilities in comparison with native cellulose fibre. Nowadays, nanocellulose is being used in a variety of practical applications such as product packaging, papers as well as paperboard, food sector, healthcare, hygiene products, paints, skin care products and sensors. The current review article summarizes the cellulose, processing methods for nanocellulose, techniques used for chemical modification of cellulose surface and consequently its application as reinforcement in polymeric materials. This article also provides a comprehensive discussion of the historical development in the area of nanocellulose.     

Superhydrophobic surfaces from sustainable colloidal systems

In recent decades, sustainable superhydrophobic surfaces from natural materials and sustainable processes have attracted increased interest due to their lower environmental footprint and potential applications in self-cleaning surfaces and biomedical devices. Although there is significant progress on selecting suitable nano and micro particles to prepare superhydrophobic surfaces, a comprehensive review on the direct use of sustainable colloidal particles (SCPs) is lacking. In this review, we highlight the recent advances on sustainable superhydrophobic surfaces using SCPs. The composition and properties, extraction methods, and chemical modifications are described, including cellulose nanocrystals, chitin/chitosan nanoparticles, and lignin nanoparticles. In addition to the physico–chemical properties and tunable dimensionality, the fabrication methodologies of superhydrophobic surfaces using modified colloids are described. Finally, the potential applications of these sustainable superhydrophobic surfaces ranging from oil/water separation, biomedical, water harvesting, biofabrication, microfluidic reactor, and food packaging are discussed together with a future perspective on the advances made.     

The role of hydrogen bonding in non-ionic polymer adsorption to cellulose nanocrystals and silica colloids

A piqued interest in nanocellulose has recently arisen due to the growing need to use sustainable and renewable materials in place of those that are derived from petrochemical resources. Although current commercial uses of nanocellulose remain limited, research over the past two decades demonstrates numerous applications including reinforcing agents in polymer and cement composites, coatings, foams, gels, tissue scaffolds, and rheological modifiers, amongst others. Because of the hydrophilic nature of nanocellulose many of the potential uses will likely be in water-based formulations or employ water-based processing methods. Thus understanding the interactions between nanocellulose and water-soluble polymers is critical. Although polyelectrolyte adsorption to cellulose is well understood, adsorption of non-ionic polymers is less clear, with hydrogen bonding often cited as a governing factor. Recent work suggests that in fact hydrogen bonding does not play a significant role in nanocellulose systems, and that non-ionic polymer adsorption is largely entropically driven. Herein we review current literature that investigates non-ionic polymer adsorption to cellulose nanocrystals (CNCs) and draw upon previous papermaking research to better understand the mechanisms involved. Additionally we analyze recent work that compares the adsorption of polyethylene glycol (PEG) to CNCs and fumed silica that provides further insight into this phenomenon. Our findings, along with current literature, suggest that hydrogen bonding does not significantly impact polymer adsorption in aqueous media despite reports to the contrary.     

二维纳米片用于快速高效膜法气体分离

膜法气体分离作为一类低能耗先进分离技术, 在化工分离中具有广阔的应用前景. 然而商业气体分离膜在实际应用过程中存在选择性和渗透性此消彼长的问题. 以二维纳米片材料为膜构筑基元, 有望突破这一瓶颈. 最具代表性的二维纳米片膜材料当属石墨烯及其衍生物、 二维沸石分子筛、 层状双金属氢氧化物、 二维过渡金属硫化物、 Mxene、 二维共价有机骨架和金属有机骨架材料. 本文对这些二维材料在超薄气体分离膜领域的成果与进展进行介绍, 展现了各类材料在实际分离应用过程中的优势及弊端, 探讨了二维纳米片膜材料在气体分离领域的挑战与发展前景.