Trimethylsilylation of Cellulose in Ionic Liquids

Trimethylsilylation of cellulose in different 1,3‐dialkylimidazolium ionic liquids (IL) with hexamethyldisilazane (HMDS) as a silylating agent was investigated. Trimethylsilyl (TMSi) cellulose with a degree of substitution (DS) greater than 1 is insoluble in the IL. The maximum DS obtained depends on the nature of the anion. Carboxylate and diethylphosphate counterions gave better results than chloride or thiocyanate, which corresponds to the solubility of HMDS in the IL. Controlled silylation with stoichiometric amounts of HMDS was feasible in imidazolium carboxylates and diethylphosphate. Analysis of the substitution pattern of the silyl groups in the anhydroglucose unit (AGU) by methylation analysis gave a more homogeneous distribution under (initially) homogeneous conditions (fewer unsubstituted AGUs, fewer trisubstituted AGUs) compared to TMSi cellulose obtained in liquid ammonia.

     

离子液体在纤维素研究中的应用

离子液体是一种新型的绿色溶剂,纤维素是一种可再生的生物资源,作为非衍生化纤维素溶剂,离子液体在纤维素研究中呈现出了良好的发展态势。本文综述了纤维素在离子液体溶解、再生、衍生化反应及其在生物酶催化等方面的一些研究成果。     

羧酸根阴离子型功能化离子液体对纤维素的溶解性能

通过两步法合成了1,3-二甲基咪唑乙酸盐([C₁mim][CH₃COO])和1,3-二甲基咪唑羟基乙酸盐([C₁mim][HOCH₂COO])两种羧酸根阴离子型功能化离子液体。 研究了纤维素在这两种离子液体中的溶解性能。 结果表明,阴离子的结构对纤维素的溶解性能有明显影响,在120 ℃下,两种离子液体对纤维素的溶解度分别为19.7%和21.2%。 通过傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)以及热重分析(TG)等技术手段对再生纤维素的结构和热稳定性进行表征,表明两种离子液体均为纤维素的直接溶剂,纤维素在溶解及再生过程中晶体结构由I型转变为无定型结构,且热稳定性有所下降。 此外,研究发现溶解温度的提高和溶解时间的延长均会导致再生纤维素聚合度的降低。 所获得的研究结果为纤维素溶剂体系的开发具有指导意义。     

复合离子液体中纤维素的催化分解

通过将酸性功能化离子液体与对纤维素具有溶解作用的离子液体进行复合, 构建了一类新型的高效催化纤维素分解的体系, 并采用热重(TG)分析方法, 研究了复合离子液体中纤维素的分解行为. 结果表明: 复合离子液体中纤维素的分解温度明显降低, 溶于离子液体中的纤维素可被酸性离子液体原位催化分解. 纤维素的分解温度受离子液体催化剂的酸性及纤维素在复合离子液体中的溶解度影响明显: 酸性越强, 溶解度越大, 纤维素的分解温度越低.     

Unconventional Reactivity of Cellulose Dissolved in Ionic Liquids

Summary: Ionic Liquids (IL) were applied as solvent and reaction medium in the field of homogeneous cellulose chemistry. Whereas investigations on tosylation and nucleophilic displacement reactions lead to unexpected products the application of the Huisgen reaction was successful. The standard conditions for tosylation of cellulose using the IL 1-ethyl-3-methylimidazolium acetate (EMImAc) as solvent lead exclusively to cellulose acetate, due to activation of the acetate ion of the IL by forming a mixed anhydride with p-toluenesulfonyl chloride. Further investigations showed that the anions of EMImAc and 1-ethyl-3-methylimidazolium chloride (EMImCl) are able to act as nucleophiles, thus substituting tosyl groups of tosylcellulose and forming unexpected products. Using EMImAc as solvent first to third generation propargyl-polyamidoamine (PAMAM) dendrons were attached to 6-azido-6-deoxy cellulose (degree of substitution, DS 0.75) utilising the copper catalysed Huisgen reaction leading to novel dendronized cellulose derivatives with DS values of up to 0.60. Detailed structure characterisation of the products, including elemental analysis, FTIR and NMR spectroscopy, indicates that the synthesis approach leads to products without impurities or remaining IL.     

纤维素在离子液体中的降解转化

随着社会对能源资源的需求越来越大,生物质资源得到了广泛的重视,世界上存储量最大的生物质资源--纤维素在新兴溶剂离子液体中的降解转化受到了越来越多的关注。本文简要介绍了近几年来纤维素在离子液体中的溶解、单糖(果糖、葡萄糖)在离子液体中脱水转化为5-HMF(5-羟甲基糠醛)和纤维素在离子液体中一步降解转化为5-HMF的研究。指出目前研究存在的缺点与不足,并提出了可能的解决方法。     

利用离子液体制备纤维素基气凝胶

纤维素基气凝胶材料的研究在近年来吸引了人们极大的关注,这是因为这类新型材料具有通常无机气凝胶的典型结构特点,如超轻、高孔率、高比表面积等,同时具有天然生物质材料的原料丰富、可再生、可生物降解的优点。本文首先简要介绍了纤维素基气凝胶材料及其发展概况,进而主要介绍了以离子液体为溶剂制备再生纤维素基气凝胶的研究进展,包括纤维素基气凝胶的制备方法、结构及其功能性。最后对离子液体法制备的纤维素基气凝胶材料的前景进行了简要的展望。     

离子液体溶解纤维素的研究

纤维素是一种可生物降解的天然高分子材料,由于纤维素含有大量的分子间和分子内氢键,导致纤维素难溶于水和一般的有机溶剂。现有的溶剂存在稳定性差、具有毒性、难以回收等缺点,对纤维素的加工、利用造成困难,因此,寻找新型绿色溶剂成为纤维素开发的热点和难点。离子液体是一种新型高效绿色溶剂,在一定条件下可以溶解纤维素、角蛋白等生物大分子,离子液体的出现为纤维素的溶解提供了一种环境友好、可生物降解的溶剂体系,具有广阔的应用前景。本文就不同种类离子液体溶解纤维素的溶解度以及影响溶解度的几种因素进行了综述,总结了离子液体与纤维素作用机理以及离子液体的回收方法,为纤维素的加工利用提供了理论依据和工业指导。     

以离子液体为介质的纤维素加工与功能化

纤维素作为自然界中储量最大的天然高分子,被认为是未来世界能源与化工的主要原料.但由于分子链间存在丰富氢键网络以及高度结晶的聚集态结构特点,天然纤维素不熔化、难溶解,造成纤维素的加工极其困难,纤维素材料的传统生产工艺复杂且污染严重,极大限制了纤维素材料的广泛应用.近年来,人们发现一些特定结构的离子液体能够高效溶解纤维素,为纤维素的加工和功能化提供了新的多用途平台.本文从"溶解纤维素的离子液体、纤维素溶解机理与溶液性质、以离子液体制备再生纤维素材料和以离子液体为介质合成纤维素衍生物"4个方面详细介绍了本课题组在此领域的研究进展.     

Electrocatalyst Fabrication Using Metal Nanoparticles Prepared in Ionic Liquids

Metal nanoparticle-based electrocatalysts are widely used in electronic devices, which serve for electrochemical reactions like oxygen reduction reaction, alcohol oxidation and CO₂ reduction reaction. These catalyst-dependent reactions are the key of the emerging clean energy systems. Catalyst design and synthesis therefore have received keen attention in past decades. We are motivated to study synthesis approaches of metal nanoparticle-based electrocatalysts using ionic liquids (ILs), which are promising solvents for the nanoparticle preparation because of their unique physicochemical properties. In this personal account, we review our previous and present works on nanoparticle preparation in IL and utilization of the obtained nanoparticles as electrocatalysts.     

Dissolution of Cellulose and Lignin with Biobased Ionic Liquids

Journal of Solution Chemistry - Choline-based ionic liquids, involving various alkyl chains lengths and carboxylates derived from biobased acids, have been synthetized with high yields through a...     

Comparison Between Two Different Synthetic Routes of Pyrrolidinium Functional Polymeric Ionic Liquids

Summary: Two separate synthetic routes of preparation of new pyrrolidinium-based polymeric ionic liquids were compared. The first method utilized the modification of a commercial poly(diallyldimethylammonium) chloride via a direct anion exchange with several anions. The second route involved the anion exchange leading to several diallyldimethylammonium ionic liquid monomers having different anions and a subsequent polymerization. The latter method is particularly interesting for attaining tunable copolymers according to the desired properties of PILs. Both methods successfully resulted in ionic liquid polymers that are finding their way in a wide range of emerging applications.     

离子液体对锯末中纤维素的溶解及再生研究

探讨了离子液体1-(4-磺酸基丁基)-3-甲基咪唑的硫酸氢盐(IL-1)作为催化剂,金属氯化物作为助催化剂时纤维素的水解,利用离子液体IL-1对杨木锯末中纤维素的直接溶解并再生,考察了温度、碱性溶液的浓度以及溶解时间对溶解率的影响,通过傅里叶红外光谱FT-IR、X-射线衍射仪及热失重对处理前后锯末、再生纤维素的结构、结晶性及热性能进行了研究.结果表明,温度为90℃,NaOH质量分数为6%,溶解时间为2 h时,离子液体对杨木锯末具有最佳的溶解性,溶解率可达45%左右.离子液体主要溶解杨木锯末中的纤维素,且为非衍生化的直接溶解,再生后的纤维素结晶形态由纤维素I变为II,热稳定性能有所降低.     

固定化离子液体吸附黄酮类化合物性能研究

研究了吸附时间、固液比、样品浓度、上样流速对N-甲基咪唑键合硅胶固定化离子液体(SilprMim)吸附黄酮类化合物性能的影响.结果表明,受试化合物在30 min内均达到吸附平衡;吸附效率随固液比增大而增加,随样品浓度增大而降低;吸附等温线与拟合的Langmuir模型吻合良好.SilprMim对染料木素、木犀草素及槲皮素的饱和吸附量分别为47.7, 52.5和63.2 mg/g,上样流速在0.5～1.5 mL/min范围内吸附效率达90%以上;甲醇洗脱染料木素、木犀草素及槲皮素的解吸率分别为86.1%, 83.3%和84.6%;解吸顺序为:染料木素、木犀草素、槲皮素.SilprMim对3种受试黄酮类化合物具有较强吸附和分离能力,有望应用于黄酮类天然产物的分离纯化.     

不同离子液体中硝基苯的电化学还原

研究了硝基苯在N-甲基咪唑对甲基苯磺酸([Mim][PhSO3])和1-丁基-3-甲基咪唑六氟磷酸([Bmim][PF6])两种离子液体中的电化学还原反应.循环伏安法测试显示,硝基苯在[Mim][PhSO3]中只出现一个还原峰,是一个受扩散控制的不可逆电化学反应,而在[Bmim][PF6]中出现两对氧化还原峰,表明其还原产物随离子液体性质的不同而异.     

纤维素在离子液体中的溶解性能及机理研究进展

综述了纤维素在离子液体中的溶解性能和机理的研究进展,总结了纤维素在离子液体中发生溶胀、溶解的物化特性;指出纤维素在离子液体中的溶解属于直接溶解,溶解温度、溶解时间、加热方式、离子液体结构及是否含水等均可影响纤维素的溶解性能;分析了离子液体体系中纤维素应用方面存在的问题,即用于溶解纤维素的离子液体种类有限,溶解机理尚无成熟和完整的理论模型,有待于进一步研究.     

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。     

Possibilities for the Physical Modification of Cellulose Shapes Using Ionic Liquids

Summary: Functional cellulose shapes offer valuable properties for innovative application potentials in textile and medical products. Thereby excellent textile physiological properties of cellulose are allowed to be connected with novel application characteristics like bioactivity, electrical conductivity, heat storage or ability to adsorb liquids or gases. A very advantageous way to modify the properties of fibres, films or textile structures is to introduce particular additives via the Lyocell process. Regard to technical applications, functional additives will be able to incorporate themselves in the shape matrix and, in the case of using N-methylmorpholine-N-oxide monohydrate (NMMO) as solvent, implicate massive technological difficulties and deterioration of properties of the spinning dope. Beside a couple of limiting moments, ionic liquids (ILs) offer as direct solvents an excellent chance for physical modification of cellulose shapes. In contrast to NMMO, they exhibit a significantly higher thermal stability as well as a higher chemical resistance. ILs exhibit most widely a better dissolving capability for a number of different polymers. First results of the development of adsorber materials as well as novel bioactive fibres will be discussed and fibre characteristics will be given.     

咪唑基离子液体非共价修饰的石墨烯结构与分散性

在离子液体氯化-1-烯丙基-3-甲基咪唑(AmimCl)存在的条件下,利用水合肼对氧化石墨烯进行同步还原,制备了一种可稳定分散在N,N-二甲基甲酰胺(DMF)和乙酸丁酯等有机溶剂中的离子液体改性石墨烯(IL-G)。运用红外光谱(FTIR)、紫外-可见吸收光谱(UV-Vis)、热失重分析(TGA)、原子力显微镜(AFM)、拉曼光谱(Raman)、X射线电子衍射(XRD)和X射线光电子能谱(XPS)对制备的改性石墨烯进行结构性能测试,结果表明离子液体AmimCl与石墨烯之间存在π-π和阳离子-π的相互作用,能较好的吸附在石墨烯表面。TGA测试表明IL-G中离子液体的比例约为7.20wt%。同时,AFM结果显示改性石墨烯剥离在DMF中的平均厚度是0.962 nm。由于非共价改性石墨烯可再分散于DMF和乙酸丁酯中,通过紫外可见吸收光谱测得其最大分散浓度分别是1.69 mg·mL-1和1.12 mg·mL-1。