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。     

石墨烯及其复合材料吸油性能研究进展

石油化工产品在国民经济生活中占有重要地位,但在石油开采和运输过程中漏油事件频发,对海洋生态环境造成重大污染.物理吸附除油方式以其成本低、污染小、可回收利用、操作简单等优点得到广泛应用.传统吸附材料往往具有双亲性,选择吸附性较差,需要进行表面疏水处理.石墨烯凭借其超大比表面积和亲油疏水的特性引起广泛关注.重点综述了石墨烯...     

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。     

纤维素基功能材料的研究进展

纤维素是自然界中最为丰富的可再生天然高分子材料,价格低廉,可生物降解,是最有潜力的绿色材料之一。纤维素分子链上含有大量羟基,形成分子间与分子内强烈的氢键网络,使得纤维素难于溶解在普通的溶剂中,难于加工,极大地限制了它的广泛应用。本文从纤维素的衍生物、接枝共聚物及凝胶的制备三方面,介绍了纤维素基功能材料的研究进展情况。通过化学改性的方法,减弱了纤维素分子间的氢键作用,得到结构与功能多样的纤维素材料,拓宽了纤维素的应用领域。     

纤维素基超润湿材料在油/水分离应用中的研究进展

本文总结了纤维素基材料在油/水分离方面应用的研究进展。 以不同润湿性表面在油/水分离中的应用为切入点,介绍了3种不同的纤维素基油/水分离材料, 并结合作者所在课题组的研究工作,重点介绍了智能响应型油/水分离材料。 同时也总结了纤维素基超润湿材料在油/水分离之外的应用。 文章最后展望了纤维素基超润湿材料未来的研究方向并提出了亟待解决的问题。     

纤维素基吸附分离材料研究进展

以纤维素为原料制备吸附分离材料可以减少对石油资源的依赖,并具有成本低、环境友好和生物相容性好等优点。利用纤维素中的羟基基团,通过交联、接枝、引入无机粒子或与聚合物复合,可以制备出微球和薄膜等不同形态的吸附分离材料,广泛应用于生物医学,废水处理、气体分离等领域。本文结合近五年来国内外纤维素及其复合材料在吸附分离领域的研究近况,从水、油、重金属、气体和有机物的应用进行了综述,总结了纤维素基吸附分离材料的研究尚存在的问题,探讨了今后的研究方向。     

纳米纤维素基多层级孔道结构碳气凝胶的制备及在锂电池中的应用

采用纳米精磨法对商品桉木浆进行纳米纤丝化处理,得到了高长径比、尺寸均一的纳米纤丝化纤维素(NFC),平均直径为230.10 nm,长度达数十微米.将其组装、干燥后制得具有大量介孔的纳米纤丝化纤维素气凝胶(NFCA).将NFCA在氮气氛围下高温碳化制得碳气凝胶(CNFA),或在氢氧化钾条件下辅助碳化制得具有多层级孔道结构的碳气凝胶(CNFA-A),在保留的碳气凝胶骨架结构上进行孔洞构建.通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)表征及Nanomeasure统计分析,发现NFC的平均直径经碳化后减小到53.16 nm.利用X射线衍射(XRD)、BET比表面积测试和拉曼光谱揭示了碳化处理对纳米纤维素结构、比表面积、石墨化程度和缺陷的影响.结果表明,KOH辅助碳化处理后的碳气凝胶不仅保留了纤维素气凝胶前驱体的网络结构,还在其骨架上二次构建了更多的微孔和介孔,其比表面积高达488.92 m2/g,总孔容为0.404 cm3/g,所得的碳骨架被部分石墨化,具有良好的导电性.这类源于生物质的高比表面积碳气凝胶在被用作锂离子电池(LIB)负极材料时表现出优异的电化学性能,在电流密度1 A/g下连续充放电1000次后比容量达到409 m A·h/g,在电流密度高达20 A/g下,比容量还能维持在219 m A·h/g.     

炭气凝胶及其有机气凝胶前驱体的研究进展

介绍了炭气凝胶及其有机气凝胶前驱体的发展概况，着重总结了制备工艺条件(如催化剂及其浓度、反应物总浓度、反应物配比、溶剂、反应温度及时间、超临界干燥工艺条件和炭化工艺条件等)对有机气凝胶及其相应炭气凝胶中孔网络结构的影响，综述了中孔网络结构改性研究的进展．     

脂肪酶催化合成纤维素-甲基丙烯酸丁酯接枝聚合吸油材料

以棉浆粕为基材,硝酸铈铵/HNO3为引发剂,甲基丙烯酸丁酯(BMA)为接枝单体,脂肪酶为催化剂,N,N′-亚甲基双丙烯酰胺为交联剂,采用悬浮震荡接枝聚合反应制备了纤维素-BMA接枝聚合吸油材料.采用红外光谱、X射线衍射、扫描电镜、热重、差热等手段对产物结构进行了表征,考察了棉浆粕的引发及其后的接枝聚合反应,得到脂肪酶催...     

以纤维素/AmimCl溶液制备纤维素气凝胶

利用离子液体AmimCl溶解结合超临界CO2干燥的方法制备了纤维素气凝胶材料.研究了不同初始浓度的纤维素溶液及其在不同凝固浴中制备的纤维素凝胶的流变行为,进一步考察了纤维素溶液浓度和凝固浴种类对纤维素气凝胶材料结构的影响.结果表明,随着初始纤维素溶液浓度的增大,气凝胶的孔结构逐渐致密,比表面积随之减小;凝固浴的组成对纤维素气凝胶的结构也有较大影响.采用适当的制备条件,可以制备出高比表面积的纤维素气凝胶材料.对纤维素气凝胶的热性能进行了表征,结果表明所得到的气凝胶材料具有较好的热稳定性和较高的炭残余含量.     

Synthesis of Oil Spill Sorbents Based on Cellulose Derivatives

In this work, hydroxypropyl cellulose (HPC) was used to synthesize hydroxypropylcellulose acrylate (HPCA) macromonomer by esterification of HPC with acryloyl chloride in homogenous solution of DMF. Then the produced HPCA monomer was copolymerized with ethylhexyl acrylate (EHA) in presence of two types of crosslinkers to produce oil gel. Several parameters were considered, namely, monomers feed ratio, type and concentration of the applied crosslinkers. The chemical structures of both HPC and HPCA were confirmed by using FTIR and ¹H NMR spectroscopic analyses. Also, the thermal properties of the crosslinked oil absorbents were investigated by using TGA. Furthermore, morphological propoeries of these crosslinked sorbers were studied through SEM and their swelling efficiency was thoroughly investigated in heavy and light oil.     

Tensile Properties and Morphology of Oil Palm Empty Fruit Bunch Regenerated Cellulose Biocomposite Films

The regenerated cellulose (RC)biocomposite films were prepared using casting method where oil palm empty fruit bunch (OPEFB) and microcrystalline cellulose (MCC) were dissolved in N-dimethylacetamide/lithium chloride (DMAc/LiCl)solution. The increasing of OPEFB contents up to 2 wt% increased the tensile strength and modulus of elasticity of RC biocomposite films while the elongation at break decreased. However, at 3 and 4 wt% of OPEFB content, the tensile strength and modulus of elasticity decreased with increases OPEFB content, but elongation at break increased. The increment of tensile strength and modulus of elasticity at 2 wt% is due to the OPEFB fiber that partially dissolved and dispersed with the OPEFB matrix. The morphology studies illustrate that at 2 wt% of OPEFB content of biocomposite films surface consists less voids and agglomerations than at 4 wt%. This can be considered the RC filler was partially dispersed with the RC matrix in the biocomposite films.     

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.     

Fabrication of Superhydrophobic Surfaces of Cellulose Sheets by Creating Biomimic Structures

The biodegradable superhydrophobic cellulose sheets were fabricated by simple dissolution, controllable crystallization, coagulation, and Teflon dip-coat. The surface morphology of the superhydrophobic regenerated cel- lulose sheets is similar to that of the natural lotus leaves consisting of hierarchical micro/nano structures. The pre- pared cellulose sheets exhibit a remarkable suoerhvdroohobicity and satisfactory long-term chemical stabilitv.     

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.     

Effect of Butyl Methacrylate on Properties of Regenerated Cellulose Coconut Shell Biocomposite Films

In this study, butyl methacrylate acid (BMA) is used as chemical modifier of regenerated cellulose (RC) coconut shell (CS) biocomposite films. The effect of CS content and BMA on tensile properties and crystallinity index (CrI) of RCCSbiocomposite films were investigated. It is found that the increasing of CS content up to 3 wt% increased the tensile strength and modulus of elasticity but decreased at higher content of CS. Elongation at break decreased with increasing of CS content and increased at 4 wt% of CS. Cystallinity index (CrI) of biocomposite films also increased with increasing CS up to 3 wt% content. At similar CS content, treated RC CS biocomposite films with BMA were found to have higher tensile properties and crystallinity index (CrI) than the untreated biocomposite films. The modification by BMA improved interfacial interaction and dispersion of CS in RC biocomposite films.     

Distribution of Substituents along the Cellulose Chain on Cellulose Xanthate and Carboxymethyl Cellulose

The distribution of substituents of cellulose xanthogenate and carboxymethyl cellulose along the cellulose chains and therefore in relation to the molecular mass can be measured using size exclusion chromatography including a multi angle laser light scattering and mass detection for determining the molecular mass of the derivative assisted by an UV- detection for determining the xanthate groups and carboxymethyl groups after derivatisation, respectively. The results investigating cellulose xanthogenate show that the temperature used in dissolving xanthogenate and in ripening viscose influences the distribution of xanthate groups in a different way; but all steps processing viscose are connected with a loss in the degree of substitution in ripening the distribution of substitution additionally becomes more even. The investigated carboxymethyl cellulose revealed different distribution of carboxylic groups in dependence on the viscosity of the CMC.     

New Possibilities of the Acetosulfation of Cellulose

Regioselectively substituted cellulose sulfates in C2/3-, C2/6-, or C6-position of the anhydroglucose unit are accessible by certain synthesis routes. Thereby, products with different properties and various application areas are resulted. Important characteristics of cellulose sulfates regarding their applications are solubility (e.g. in water), rheological behavior, different interaction with low or high molecular cations, thermo reversible gel formation, enzymatic degradability, anticoagulant and antiviral activity. In C6-position substituted cellulose sulfates can be synthesized in principle by acetosulfation. The acetosulfation is a quasi-homogeneous synthesis proceeding under gradually dissolution of the cellulose by using different reactivity of the primary and secondary OH-groups as soon as converting cellulose acetate sulfates. After precipitation of the polymer the acetyl groups are cleaved in alkaline solution. The focus of our study was firstly the investigation of the acetosulfation in different polar aprotic solvents by various sulfating and acetylating agents. In general it should be investigated if C6 substituted cellulose sulfates can be obtained by acetosulfation with different solvents and agents. The products were characterized by ¹³C-NMR and Raman spectroscopy.     

细菌纤维素纳米纤维稳定乳液的性能

采用超声和高压均质两种方式分散的细菌纤维素(BC)悬浮液制备了BC纳米纤维稳定的水包油型Pickering乳液, 并考察了纤维用量、 pH值和机械分散方式对乳液稳定性的影响. 结果表明, 乳液的稳定性随纳米纤维用量的增加而增加; 碱性条件比酸性条件制备的乳液稳定性高, 且在pH=12时达到最高. 用高压均质方式分散的BC稳定乳液的效果优于采用超声方式分散的BC的效果, 这是由于高压均质后的纤维较短, 可以提供更多的纳米纤维稳定乳液. 计算结果表明, BC纳米纤维在液体石蜡/水界面上的三相接触角为72.5°, 说明BC适合稳定水包油型乳液.