细菌纤维素复合材料的研究新进展

细菌纤维素是一种新型的纳米级材料,具有高吸水性、高纯度、高结晶度和良好的生物相容性.本文综述了细菌纤维素复合材料在医疗、化工以及食品包装这3个重要领域的研究现状及其代表性成果,提出了利用聚合物渗透、掺杂原子和纳米颗粒修饰等方法制备新型细菌纤维素纳米复合材料,克服单一细菌纤维素材料性能上的缺陷,为其在更多领域的应用提供了思路.     

细菌纤维素在包装领域的研究进展

目的 将来源于自然的细菌纤维素作为包装材料应用于包装领域,以取代传统的塑料包装材料.方法 综述近几年细菌纤维素在包装领域的研究与应用现状,介绍细菌纤维素的基本培育过程、改性技术和制备方法,阐述细菌纤维素在包装领域的研究与应用.结果 细菌纤维素通过层层组装、聚合、联接等方式,可与多种聚合物高效复合,形成不同微观尺寸和结构特性的纤维素基多孔复合材料,从而改善其力学性能和物理性能,并可调控其阻隔性能和抗菌灭菌性能.常用细菌纤维模式为纳米细菌纤维和纳米细菌晶须.结论 细菌纤维素材料及其复合材料完全可以替代塑料用于包装领域,在食品包装和智能包装上的研究和应用前景较大.     

细菌纤维素/银纳米粒子复合多孔支架材料的制备与表征

以细菌纤维素水凝胶膜、硝酸银和硼氢化钠为原料,制备了细菌纤维素/银纳米粒子多孔复合支架,并利用扫描电子显微镜、能谱分析、X射线衍射、热失重及力学性能测试对多孔复合支架进行研究。结果表明,在细菌纤维素网络结构内部发现了银纳米粒子,表明银纳米粒子进入到细菌纤维素内部,形成细菌纤维素/银纳米粒子复合物;并且,银纳米粒子的粒径随着硝酸银和硼氢化钠浓度的升高而变大;银粒子的引入使细菌纤维素的链规整度有所下降,结晶度变小、力学性能下降,但材料具有了良好的抗菌性能,使其更适用于医用敷料领域。     

纳米纤维素基复合材料及其用于柔性储能器件的研究进展

纳米纤维素是一类具有大比表面积、高反应活性、高机械强度、良好生物相容性、优异热稳定性以及可降解等优异性能的纳米高分子材料。根据其来源、特性、制备方法,可大致分成纤维素纳米纤丝(CNF)、纤维素纳米晶体(CNC)、细菌纤维素(BC)三类,三者的微观形态和尺寸大小有所差异。纳米纤维素凭借其高抗张强度,在复合增强材料的填充应用上表现出优异的机械柔韧性,借此将其与导电聚合物、碳材料和金属化合物等导电物质复合,可形成具有优异力学性能和电化学性能的导电复合材料,这类材料在柔性储能器件等领域有着广泛的应用前景。本文重点回顾了纳米纤维素与多种导电物质复合制备导电复合材料的工艺方法及电化学性能表征,并概述了基于纳米纤维素的导电复合材料在柔性储能器件锂离子电池(LIBs)和超级电容器(SCs)上的应用研究进展,在总结相关研究的基础上进一步讨论了上述制备应用过程中存在的问题,并针对此类问题展望了纳米纤维素基导电复合材料在今后研究应用的重点和方向。     

细菌纤维素抗菌复合材料的制备和应用

目的 综述细菌纤维素抗菌复合材料在国内外的研究和应用现状,以制备具有优异抗菌性能的细菌纤维素复合材料.方法 总结细菌纤维素抗菌复合材料的抗菌性及其最新合成方式,包括与无机抗菌剂、有机抗菌剂结合或添加抗生素等方式合成细菌纤维素抗菌复合材料,并进一步阐述细菌纤维素抗菌复合材料的应用领域.结论 细菌纤维素复合材料的抗菌性能优异,在医学、食品包装和净水等领域都有较大的应用潜力,有待进一步系统研究.     

纳米纤维素基材料在柔性电子器件中的应用

目的 由于纳米纤维素基材料良好的柔韧性、热力学性能和高透明度,近年来在柔性电子产品中引起越来越多的关注。通过综述该领域的研究进展,将有助于研究人员更高效地开展研究。方法 综述3类纳米纤维素的制备方法及将纳米纤维素基材料应用在柔性电子产品中的研究进展。分别阐述纳米纤维素基材料应用于器件柔性衬底及绝缘材料的研究实例,并讨论纳米纤维素在各种应用方向中的优势以及存在的问题,最后对材料的未来应用前景进行展望。结论 纳米纤维素是天然纤维素与纳米技术结合的产物,可主要划分为纤维素纳米纤丝、纤维素纳米晶以及细菌纤维素3类。近年来,纳米纤维素基材料作为电子器件柔性衬底、绝缘材料等研究均有许多成果问世。虽然纳米纤维素基电子器件的开发还主要停留在实验室阶段,但是与传统的石油化工产品相比,纳米纤维素具有原材料丰富、环保可降解等优点。对纳米纤维素基新型材料的开发利用,有助于解决人类社会中日益严重的电子垃圾问题。     

纳米纤维素在气体阻隔包装材料中的应用进展

目的介绍纳米纤维素在包装中的应用与国内外的研究现状,阐述纳米纤维素在改善包装材料气体阻隔性能方面的作用机理、作用方式及作用效果,并对纳米纤维素在气体包装材料领域中的应用前景进行展望。方法归纳整理国内外文献,简单介绍纳米纤维素的基本性能和制备,以及纳米纤维素复合材料的制备方法,并重点整理分析纳米纤维素复合材料在阻隔包装材料领域的应用与进展。结果纳米纤维素具有来源广泛、可降解、可再生以及高结晶度等优良特性,在包装材料中加入纳米纤维素可以显著提高包装材料的气体阻隔性能。结论随着对纳米纤维素研究的不断深入,纳米纤维素在气体阻隔包装材料中的应用会越来越广泛。     

细菌纤维素纳米棒阵列的制备

室温下,以细菌纤维素为基础材料,在其二甲基乙酰胺和溴化锂混合溶剂中,用溶剂挥发法,制得细菌纤维素纳米棒阵列。探讨了基底对形成细菌纤维素纳米棒阵列的影响。初步研究了细菌纤维素纳米棒阵列的形成机理。     

细菌纤维素基磁性纳米复合材料的研究进展

细菌纤维素作为一种新型的生物纳米材料,不同于植物纤维素,其较高的比表面积、精细的三维纳米网状结构和表面大量的活性反应位点可以作为"模板"反应使用,通过原位复合的方法可有效地控制、合成具有预期特定形貌与尺寸且分布均匀的磁性纳米复合材料,从而获得良好的综合性能。从细菌纤维素作为"模板"制备功能化材料的机理出发,归纳总结了近年来细菌纤维素基磁性材料的研究进展,着重归纳了解决磁性膜材料的颗粒团聚问题的方法,并展望了细菌纤维素基磁性材料的发展趋势。     

纳米纤维素在功能纳米材料中的应用进展

纳米纤维素分为纤维素纳米纤维(CNF)、纤维素纳米晶体(CNC)、细菌纳米纤维素(BNC)。CNF主要由机械法和2,2,6,6-四甲基哌啶-1-氧基(TEMPO)介导氧化法制备,呈微纤丝状。CNC主要由酸水解法制备,呈棒状或针状颗粒。BNC由细菌合成,呈纳米纤维网络状。文中综述了纳米纤维素在凝胶、仿生复合材料、导电材料、电极材料、导热材料、电磁屏蔽材料、压电材料及传感器材料领域的应用现状,并对其功能纳米材料未来发展的方向进行了展望。     

细菌纤维素/壳聚糖复合多孔支架材料的制备与表征

利用细菌纤维素水凝胶膜和壳聚糖为原料,介绍了多孔复合支架的制备方法,并利用红外光谱、扫描电子显微镜、X射线衍射、元素分析及力学性能测试对多孔复合支架的特性进行了研究。结果表明,复合多孔支架的表面孔径变大、孔隙率下降,但依然呈三维网络结构;壳聚糖的加入有可能取代水分而与细菌纤维素分子链形成分子间相互作用,使细菌纤维素的链规整度下降,结晶度指数由0.82下降至0.61;力学性能有所下降,拉伸强度从140MPa下降至134MPa;这种复合多孔支架由于具有良好的生物相容性可以应用于生物医学领域,如辅料、组织工程支架等。     

氧化细菌纤维素的制备及其表征

目的 通过高碘酸钠氧化制备含醛基的氧化细菌纤维素,并改善细菌纤维素的抗菌性能,为细菌纤维素的综合利用提供新思路.方法 以氧化细菌纤维素中醛基的含量和保留率作为评价指标,通过单因素和正交试验对其进行优化,利用红外光谱仪、扫描电镜对氧化前后的细菌纤维素结构进行表征,以大肠杆菌、金黄色葡萄球菌为实验菌种,探究氧化细菌纤维素的抑菌性能.结果 当高碘酸钠浓度为0.3 mol/L,悬浮液pH为4.0,体系温度为50℃,反应时间为4.0 h时,制备的氧化细菌纤维素的最佳醛基含量为98％(质量分数)、保留率为78％.经氧化后,氧化细菌纤维素存在醛基官能团,其对大肠杆菌、金黄色葡萄球菌产生的抑菌圈直径分别为21.5,23.3 mm.结论 制得了含醛基的氧化细菌纤维素,且其具有较好的抗菌性.     

The structure and mechanical properties of sheets prepared from bacterial cellulose

A sheet obtained from bacterial cellulose had a remarkably high modulus of elasticity as reported in Part 1 of this series. The Young's modulus of a sheet prepared by squeezing and drying a gel-like pellicle of bacterial cellulose was found to be > 15 G Pa. In addition, it has been found that treatment of the gel-like pellicles or dried sheets of bacterial cellulose with alkaline and/or oxidative solutions improves the mechanical properties significantly, and the Young's modulus of the resulting sheets approaches 30 G Pa. In this paper, improvement of the mechanical properties of bacterial cellulose sheets by the removal of impurities is investigated and the applicability of bacterial cellulose to diaphragms of electroacoustic transducers is discussed.     

Novel Biodegradable and Biocompatible Poly(3‐hydroxyoctanoate)/Bacterial Cellulose Composites

Novel poly(3‐hydroxyoctanoate), P(3HO), and bacterial cellulose composites have been developed. P(3HO) is hydrophobic in nature whereas bacterial cellulose is extremely hydrophilic in nature. Therefore, homogenized bacterial cellulose has been chemically modified in order to achieve compatibility with the P(3HO) matrix. Modified bacterial cellulose microcrystals and P(3HO) have been physically blended and solvent casted into two‐dimensional composite films. Mechanical characterization shows that the Young's modulus of the P(3HO)/bacterial cellulose composites is significantly higher in comparison to the neat P(3HO) film. The melting temperature (T_m) of the composites is lower while the glass transition temperature (T_g) is higher than the neat P(3HO) film. Also, the composite film has a rougher surface topography as compared to the neat P(3HO) film. A month's in vitro degradation study has been carried out in Dulbeccos modified eagle medium and in phosphate buffer saline. The incorporation of modified bacterial cellulose microcrystal in the P(3HO) film has increased the degradability of the composite film. Finally, in vitro biocompatibility studies using human microvascular endothelial cells established the biocompatibility of the P(3HO)/bacterial cellulose microcrystal films. The cell proliferation was 50–110% higher on the P(3HO)/bacterial cellulose composites as compared to the neat P(3HO) film. Hence, in this study, for the first time, P(3HO)/bacterial cellulose composites have been developed. The addition of bacterial cellulose has resulted in properties that are highly desirable for medical applications including the development of biodegradable stents.     

细菌纤维素在NMMO·H20中的溶解性能

研究了细菌纤维素在N-甲基吗啉-N-氧化物的一水合物(NMMO·H2O)中的溶解性能,通过偏光显微分析(PM)、红外光谱分析(FT-IR)、X射线衍射分析(XRD)、热重分析(TG)等手段,表征了该溶剂体系获得的再生细菌纤维素膜的结构和性能.结果表明,该溶剂体系对细菌纤维素有良好的溶解性能,溶解过程以物理变化为主,溶解...     

细菌纤维素增强水泥复合材料的制备及性能

对细菌纤维素增强水泥复合材料进行研究,探讨细菌纤维素含量、长度对水泥基复合材料抗折、抗压强度的影响以及细菌纤维素对水泥凝结时间和水化过程的影响。结果表明:细菌纤维素的加入能明显改善水泥基复合材料力学性能,细菌纤维素质量分数为0.02%是实验最佳掺量,材料抗折、抗压强度分别提高了20%和8%;过长细菌纤维素将导致分散不均,使浆体结构疏松;细菌纤维素对水泥浆体pH值和凝结时间无明显影响;细菌纤维素促进水化过程中CaO-SiO2-H2O凝胶生成。     

Novel bacterial cellulose–acrylic resin nanocomposites

The preparation and characterization of new nanocomposite films based on two acrylic emulsions, composed of random copolymers of butyl acrylate and methyl methacrylate, and bacterial cellulose is reported. The new composite materials were obtained through a simple and green approach by casting water-based suspensions of the acrylic emulsions and bacterial cellulose nanofibrils. The excellent compatibility between these matrices and the natural reinforcing fibers, observed by scanning electron microscopy (SEM), was reflected in the enhanced thermal and mechanical properties of the ensuing composites. Thus, an increase of around 30 °C in the maximum degradation temperature was observed for a 10% content of bacterial cellulose. The new composites showed glass–rubber transition temperature profiles comparable to those of the pristine matrices, as shown by DMA, and increasing elastic moduli with increasing the bacterial cellulose content. The tensile tests revealed a substantial increase in Young’s modulus and tensile strength and a corresponding decrease in elongation at break with increasing bacterial cellulose load.     

In situ tunability of bacteria produced cellulose by additives in the culture media

Bacterial cellulose offers several advantages over other celluloses not only in terms of purity and properties but also because it allows modifications during synthesis (in situ modification). This possibility has been explored in this paper to tune bacterial cellulose in terms of cellulose microfibril dimensions, branching, crystallinity, crystallite size and porosity. It has been shown that modifiers can be added to the bacterial cell culture medium to obtain these variations during the cellulose biosynthesis. The effects of four of the several possible modifiers have been reported, namely calcofluor (dye used for cellulose), carboxy methyl cellulose (cellulose derivative), polyethylene glycol and nalidixic acid (antibiotic). Crystallinity was found to decrease from over 80 % for unmodified cellulose to about 50 % for that modified by calcofluor. The crystallite size also decreases, but to different extents along the different crystal directions, on modifications. The microfibril dimensions were found to decrease from 65 nm in case of unmodified cellulose to about 30 nm in case of carboxy methyl cellulose modification. The cellulose modified with polyethylene glycol does not show much change in crystallinity, crystallite size and microfibril dimension. Porosity was also found to decrease in all cases except that modified by polyethylene glycol where it increased from 79 to over 110 m²/g. All these observations are explained on the basis of the effect of modifier on cellulose polymerization and assembly.