细菌纤维素生物医学材料的现状及展望

细菌纤维素是由细菌合成的纯净纳米纤维素构成的网状纤维,具有优良的形态学、生物学、物理学性能以及合成可控性,因此在生物医学材料领域被广泛应用。介绍了近年来细菌纤维素应用于敷料、人造皮肤、组织修复材料和膳食纤维等方面的研究进展,并对其生物降解能力、生物相容性和纤维定向等性能的提高作出了展望。     

捏合法与淤浆法生产的PAC抗滤失性能的比较

采用中海油田新标准实验方法,研究了捏合法与淤浆法制取的羧甲基纤维素的应用性能差别,分析了其内在原因。结果表明,由于合成过程的介质种类与用量的差异,淤浆法制取的羧甲基纤维素产品比捏合法产品的取代均匀性和使用性能都有所提高,其应用性能更符合中海油新标准的要求。     

专利角度中发酵生产细菌纤维素材料的应用与发展

细菌纤维素与天然纤维素组成相似,具有较好的物理、化学和机械性能。本文从专利角度分析了有关细菌纤维素的合成和应用方向的整体发展趋势,并对涉及细菌纤维素应用的具体类型进行系统分析,为充分利用细菌纤维素开展新技术、研发新产品提供一定的参考。     

羧甲基纤维素纳米二氧化硅复合物制备及其结晶行为

羧甲基纤维素(CMC)是纤维素中羟基被羧甲基部分取代后的产物,取代后纤维素原有的结晶结构被破坏,羧甲基纤维素为非晶态结构。采用高分子表面活性剂聚二甲基二丙烯氯化铵改性纳米二氧化硅表面,以提高其与高分子材料的相容性,使其与羧甲基纤维素复合制备结晶型羧甲基纤维素。经红外光谱(FT-IR)、扫描电子显微镜(SEM)、热重分析(TGA)分析,对复合前后的结构形态进行比较,复合物尺寸大于100nm,因此它不是纳米复合物,但发现得到了羧甲基纤维素结晶,且热性能有了提高。     

硝化细菌纤维素的制备及表征

以细菌纤维素为原料,用硝硫混酸法合成出硝化细菌纤维素(NBC)。结果表明,采用硝硫混酸法合成硝化细菌纤维素未造成细菌纤维素的网状结构明显断裂降解,且合成出的硝化细菌纤维素安定性能达到A级硝化纤维素标准。用差示扫描量热法对产物进行了表征,并计算出硝化细菌纤维素的热分解活化能为212.53kJ/mol,表明硝化细菌纤维素热的稳定性优于硝化棉。     

国内简讯

国内简讯羟乙基羧甲基纤维素的合成羟乙基羧甲基纤维素（ＨＥＣＭＣ）是天然纤维素经过化学改性──醚化后获得的一类高分子化合物，是在纤维素结构单元中既含有羧甲基离子又含有非离子的羧乙基纤维素的混合醚。液相法合成ＨＥＣＭＣ是使碱纤维素和环氧乙烷在液相稀释剂中...     

羧甲基纤维素-单宁基吸附树脂的制备及性能研究

制备了羧甲基纤维素-单宁基吸附树脂,并研究了吸附树脂对亚甲基蓝的吸附性能。羧甲基纤维素与单宁结合,通过羧甲基纤维素羧基与单宁酚羟基的协同作用,能有效提高吸附树脂对亚甲基蓝的吸附性能,最大吸附容量可达1 300 mg/g。在亚甲基蓝溶液初始质量浓度为1 000 mg/L,吸附剂投加质量浓度为1.5 g/L时,吸附树脂对亚甲基蓝的吸附率可达98%以上,且羧甲基纤维素-单宁基吸附树脂具有较好的重复使用性能。     

稻草芦苇及其浆料制备羧甲基纤维素的比较

研究了直接由草粉或浆料制备羧甲基纤维素钠的溶剂适应性,并对产品的结构、粘度、取代度做了分析。结果表明,丙酮做溶剂时羧甲基纤维素合成的得率最高、取代度最大。草粉和草浆在丙酮溶剂中经过一次反应得到的羧甲基纤维素取代度均可达0.7以上。红外光谱表明,从草粉和从浆料制得的羧甲基纤维素样品结构上没有明显差别。以不同程度预处理的草粉为原料,可以得到取代度0.5~1.1之间的不同品质的羧甲基纤维素产品。     

羧甲基纤维素在陶瓷釉浆中的应用

通过对羧甲基纤维素作用机理、性能特点的分析,讨论陶瓷墙地砖生产中釉浆添加剂羧甲基纤维素的正确使用及选型应注意的关键问题。     

部分羧甲基纤维素合成及结构与性能[摘]

水——有机体系下合成了部分羧甲基纤维素。在规定的温度下考查了催化剂NaOH和醚化剂一氯乙酸以及时间、体系含水量对取代度影响。并用IR,x—射线衍射仪、DSC对产物结构和性能怍了表征,     

Cellulose as a renewable resource for the synthesis of wood consolidants

Crosslinkable cellulose ethers as allyl cellulose, allyl carboxymethyl cellulose, and allyl n‐hydroxypropyl cellulose were synthesized and characterized, and their use as consolidating agents for waterlogged wood was studied. For this kind of application, structural properties similar to those of wood's polysaccharide components are desired in the design stage of new consolidants. The choice to synthesize cellulose ethers was determined from the possibility of using cellulose as the starting material because of its large availability in nature, biocompatibility, and low cost. In addition, cellulose ethers are quite easy to obtain, and they can have different properties, depending on the nature and the amount of the functional groups introduced. For this purpose, a cellulose with a lower degree of polymerization was also used for the synthesis of related cellulose ethers. By means of Fourier transform infrared spectroscopy, the affinity of the cellulose derivatives for degraded lignin flours was detected. The preliminary results of this study show that these polysaccharide compounds may be proposed as wood consolidating agents. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Structure and properties of polysaccharide nanocrystal-doped supramolecular hydrogels based on Cyclodextrin inclusion

Polysaccharide nanocrystals, such as the rod-like whiskers of cellulose and chitin, and platelet-like starch nanocrystals, were for the first time incorporated into supramolecular hydrogels based on cyclodextrin/polymer inclusion in order to enhance mechanical strength and regulate drug release behavior. The structures and properties of the resultant nanocomposite hydrogels were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and rheological testing. As expected, the elastic modulus of the nanocomposite hydrogels climbed, owing to the reinforcing function of the polysaccharide nanocrystals. The modulus of the cellulose whisker-doped hydrogel was 50 times higher than that of the native hydrogel. Furthermore, the presence of polysaccharide nanocrystals increased the stability of the hydrogel framework and inhibited the diffusion of bovine serum albumin, which served as a model protein drug in the nanocomposite hydrogels and showed prominent sustained release profiles. Importantly, the incorporation of polysaccharide nanocrystals did not show additional cytotoxicity as comparison with the native hydrogel. In addition, the inherited shear-thinning property of the nanocomposite hydrogels contributed to their potential as injectable biomaterials.     

Wasserabsorptionseigenschaften natürlicher polyionenkomplexe

As the cationic component of natural polymer polyionic complexes, polysaccharide chitosan or polypeptide polylysine, and as the anionic component, polysaccharide carboxymethyl cellulose (=CMC) or polypeptide poly(glutamic acid) (PGA) were used. The degree of chitosan/CMC or polylysine/PGA complex film swelling was minimum, when the amounts of the cationic and anionic groups in these polymers were balanced at 1 : 1 ratio. On the other hand, the degree of chitosan/PGA film swelling was minimum at the ratio with excess of PGA which is a linear flexible chain. Comparing the enthalpies estimated by DSC analysis, it was suggested that the larger quantity of water in the form of nonfreezable bound water was absorbed in the complex films with polysaccharide which is a chain of ring structure. Further, the compressive moduli of swollen complex films were high, when the complex consisted of polysaccharide components.     

Surface modification of natural substrates by atom transfer radical polymerization

Surface modification of various solid polysaccharide substrates was conducted by grafting methyl acrylate (MA) and styrene via atom transfer radical polymerization (ATRP) to produce well‐defined polymer grafts. The hydroxyl groups on the surfaces of the substrates were reacted with 2‐bromoisobutyryl bromide followed by graft copolymerization under ATRP conditions. The studied substrates were filter paper, microcrystalline cellulose, Lyocell fibers, dialysis tubing, and chitosan films. The modified substrates were analyzed by FT‐IR, water contact angle measurements, TGA, and SEM. FT‐IR characterization of the grafted substrates showed significant differences between the different substrates in the amount of grafted polymer. Higher amounts of polymer seem to be possible to graft from native cellulose substrates than from regenerated cellulose substrates. To investigate whether the grafted polymers were “living” after a longer time period, a second layer of polystyrene was grafted from a filter paper modified with PMA one year ago. FT‐IR characterization of the filter paper showed a peak corresponding to styrene, indicating that a block copolymer had been formed on the surface. Graft copolymerization can be used to change and tailor the surface properties of the polysaccharide substrates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4155–4162, 2006     

微波辐射法在多糖接枝共聚中的应用

多糖是一种可用于合成高性能高分子材料的天然可再生资源,在自然界中蕴藏丰富。天然多糖接枝合成聚合物是制备多糖基材料的一种简便通用的方法。对目前天然多糖研究中存在的问题,接枝共聚的概念和目的,微波辐射法原理进行了介绍。同时对微波辐射法在壳聚糖、藻酸钠、纤维素、淀粉、黄原胶、瓜尔胶等多糖分子接枝中的实际应用进行了综述。     

Biosynthesis and characterization of bacteria cellulose–alginate film

A novel polysaccharide membrane containing alginate in bacterial cellulose matrix was synthesized by Acetobacter xylinum under static conditions using a culture medium supplementation with sodium alginate. By increasing alginate content, the bacterial cellulose–alginate (BCA) membrane was more hydrophilic and the film structure became denser with the smaller average pore size. Scanning electron microscope images displayed the deposits of alginate gel on the surfaces of the multilayer cellulose film. The declines in the tensile strength, the Young's modulus, and the elongation at break of the BCA membrane were dependent on the degree of alginate supplement. The BCA membrane showed higher water absorption capacity. The addition of alginate slightly affected the water vapor transmission rate but remarkably decreased the oxygen transmission rate of the membrane. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

1,2‐propanediol–cellulose–acrylamide graft copolymers

1,2‐Propanediol–cellulose–acrylamide graft copolymers (PCACs) were developed for enhanced oil recovery. They were prepared with acrylamide and 1,2‐propanediol (PDO)–cellulose, which was formed through the addition of glycols to cellulose by the Shotten–Baumann reaction between 3‐chloro‐1,2‐propanediol and cellulose. The graft copolymerization was initiated with a redox system between Ce⁴⁺ and glycols in cellulose. The infrared spectrum of PDO–cellulose had some characteristic absorption bands around 2960 (νC? H) and 1050 cm^?1 (νC? O) that also appeared for the PDO group and pyranose ring of cellulose, respectively. The rate of Ce⁴⁺ consumption by PDO–cellulose was investigated through the calculation of the overall kinetic constant from the slopes of ln(D ? D_R) versus time (where D is the absorbance and D_R is the absorbance of the original polysaccharide solution) The results showed that PDO–cellulose had high reactivity and that there were two mechanisms of oxidation by Ce⁴⁺ with PDO–cellulose. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3022–3029, 2004     

The Influence of Different Substitution Levels of Guar on the Quality of Viscose Prints with VS Monoreactive Dye

Abstract

The basic problem of reactive printing on viscose with polysaccharide guar thickeners is the capability of dye molecule to react with the hydroxyl groups of cellulose (binding of the dye) as well as with the hydroxyl groups of water (the dye hydrolyzes) or the thickener (binding of the dye) (1, 2]. This latter is most clearly expressed in combination of the polysaccharide unmodified guar thickener and the bifunctional reactive dye where the bifunctional dye forms, due to the presence of two reactive groups, a bridge between the cellulose fibre and the guar thickener (3). The unmodified guar has a large number of free hydroxyl groups which cause crosslinking with cellulose and hinder the thickener to wash off, thus increasing the stiffness of the printing fabric. The further investigation has shown that this undesireous reaction with the guar molecules can be partly diminished by the suitable selection of chemically modified guar thickener or by lowering the dry substance content [4, 5].

In this paper the influence of nonsubstituted and different substitutited guar thickeners with monoreactive (vinylsulphone) dyes on the changing of fabric stiffness will be shown.     

Extracellular Polymeric Substances in Fouling Layer

Abstract

Membrane biofouling via microbial products limits the feasibility of utilizing membrane bioreactor (MBR) for treating wastewater. Fouling layer would be built up when activated sludge was filtered with a mixed cellulose ester membrane. This study probed the three‐dimensional distributions of protein, α‐polysaccharide, and β‐polysaccharide in fouling layer using fluorescently labeled lectins and fluorescein isothiocyanate (FITC) as staining agents in combination with confocal laser scanning microscopy (CLSM). These extracellular polymeric substances (EPS) distributed heterogeneously in the fouling layer, with α‐polysaccharide being concentrated close to the membrane surface. The flow pattern yielded in the fouling layer determines the filtration resistance of biofouling.     

木聚糖生物转化药物、能源和化工中间体

介绍了木聚糖的结构与酶糖化机理,综述了国内外对木聚糖生物转化方面的研究.详细介绍了木聚糖转化为低聚木糖和木糖醇等医药食品、燃料乙醇和2,3-丁二醇等能源物质、乳酸和糠醛等化工中间体的研究进展.