【作者】 李荣吉；

【导师】 姚菊明；

【作者基本信息】 浙江理工大学 ， 材料学， 2010， 硕士

【摘要】 桑树韧皮是一种极具利用价值的新型天然资源,在本实验中,采用预处理—130°C高温高压碱煮—漂白三道工序,制得了桑皮纤维,随后通过64 wt%的硫酸水解30 min制得了桑皮纤维素纳米晶须悬浮液。根据GB5889-86《苎麻化学成分定量分析方法》分析了脱胶前后桑皮纤维中各化学组成成分的含量,发现脱胶后的桑皮纤维中,半纤维素、果胶和木质素等杂质的含量已经非常低了,FT-IR和XRD的结果也证明了脱胶过程中这些杂质的去除。同时因为在酸解中纤维素的无定形部分被水解,而释放出了纤维素单晶,最后制得的纤维素纳米晶须的结晶度高达73.4%。但是因为在水解中纤维素分子上接上了磺酸基团,因而纤维素纳米晶须的热稳定性要比桑皮纤维差很多,而且经历了低温分解和高温分解两个阶段。这种纤维素晶须的用途非常广泛,可以作为一种增强剂、也可以在药品或光学器件中作为一种添加剂。将桑皮纤维素纳米晶须来作为经过聚乙二醇增塑后的丝素膜的增强剂,最后制得了一种兼有较好的拉伸强度和柔韧性的丝素复合膜。通过场发射扫描电镜观察到纤维素晶须均匀地分散在丝素基质中,但是当晶须的含量为15 wt%时,纳米粒子出现了部分团聚。FT-IR和XRD结果表明,聚乙二醇和纤维素晶须的加入诱导了丝素蛋白的二级结构的转变,力学拉伸测试表明,在较低的晶须含量下,随着纤维素晶须含量的增加,丝素复合膜的拉伸强度不断增加,断裂应变不断减小。动态机械分析(DMA)表明,刚性的纤维素晶须与丝素基质的作用限制了无定形区的丝素多肽链在玻璃化转变时的自由运动。最后,研究了MG-63细胞在这种生物复合膜上的黏附和增殖情况,发现加入了聚乙二醇和桑皮纤维素纳米晶须后,改变了丝素复合膜的表面微观形貌等表面性能,使得纳米复合膜具有良好的生物相容性。更多还原

【Abstract】 A kind of cellulose whiskers were extracted from the branch-barks of mulberry (Morus alba L.) by an alkali treatment at 130°C and subsequently a sulfuric acid hydrolysis. AFM image showed that the diameter of obtained whiskers was ranged from 20 nm to 40 nm. The chemical compositions analysis, FT-IR, XRD results indicated that the hemicellulose and lignin were removed extensively in the cellulose whiskers, with a crystallinity of 73.4%. The TGA curves implied a two-stage thermal decomposition behavior of cellulose whisker due to the introduction of sulfated groups into the crystals in the sulfuric acid hydrolysis process. The obtained whiskers may have the potential applications in the fields of composites as a reinforcing phase, as well as in pharmaceutical and optical industries as additives.The flexible and transparent composite films were fabricated by a mixture of silk fibroin, poly(ethylene glycol) and mulberry cellulose nanowhiskers. The cellulose nanowhiskers were uniformly dispersed in the matrix when its content was as high as 12 w/w%. The tensile properties of composite films generally depended on the nanowhisker content, but significantly improved when compared with the pure SF film. DMA analysis revealed that the alpha transition temperature increased gradually with the increase of nanowhisker content, probably due to the formation of interactions between the nanowhiskers and the silk fibroin molecular chains, leading to the mobility reduction of the amorphous silk fibroin. A preliminary biocompatibility study of the nanocomposite films was carried out and the results showed an increment of MG-63 cell numbers attached on the MCW filled films and the morphologies of cells on them looked more flatten and spread, which are attributed to the much more complex surfaces properties of the nanocomposites. This kind of flexible silk fibroin-matrix composite films may possess the potential utilizations in the extended biomedical application fields.更多还原