Preparation and Structural Analysis of Nanocomposites of Bacterial Cellulose and Native Inorganic Material

为了制备一种环保新型材料，制备了由纤维素微原纤维和伊莫戈柳石纳米管组成的纳米复合材料，并对其结构和性能进行了研究。首先，被膜纤维素作为纤维素样品。经硫酸处理得到的被膜纤维素微原纤维呈棒状，长1.9 μm，平均宽25 nm。imogolite凝胶膜的原料采集自岩手县北上市Murasakino的浮石床。纯化后的imogolite纳米管外径为2.5 nm，平均长度为0.18 μm。采用偏光显微镜和扫描电镜研究了不同质量比的被膜纤维素微原纤维/伊莫高岭石纳米管在pH=3的乙酸水溶液中的液晶结构。铁长石液晶的织构表现为手性向列指纹图谱，而纤维素微纤维的织构则表现为交叉口指纹图谱。不同重量比的混合物的液晶结构都不同于单一成分的伊莫戈柳石或纤维素微原纤维的结构。利用x射线衍射分析和FT-JR研究了由不同液晶相制备的纳米复合膜的结构。室温下，纤维素、5/5、4/6和3/7纳米复合材料薄膜的储存模量E′分别为9.6、11、13、15 GPa。5/5纳米复合材料和纤维素膜的E′值对25℃以上的温度不敏感。5/5纳米复合膜在290℃下破碎，纤维素膜在250℃下破碎。通过添加铁长石改善了材料的热性能。在囊状膜/伊莫戈柳石纳米复合材料的基础上，对细菌纤维素/伊莫戈柳石纳米复合材料进行了研究。

To fabricate an environmentally friendly and new material, nanocomposites composed of cellulose microfibrils and imogolite nanotubes were prepared, and their structure and properties were investigated. First, tunicate cellulose was used as a cellulose sample. Tunicate cellulose microfibrils prepared by sulfuric acid treatment were rodlike in appearance, 1.9 μm long and 25 nm wide on the average. Raw materials of imogolite gel films were collected from a pumice bed at Murasakino, Kitakami-shi, Iwate-ken. Purified imogolite nanotubes with an outer diameter of 2.5 nm were estimated at 0.18 μm long on the average. Liquid crystal structures of the mixtures of tunicate cellulose microfibrils/imogolite nanotubes with different weight ratios in the aqueous solution of acetic acid (pH=3) were studied by polarizing optical microscopy and SEM. The texture of liquid crystal of imogolite showed a chiral nematic fingerprint pattern, while that of cellulose microfibrils gave cross-hatch pattern. All the textures of liquid crystals of the mixtures with different weight ratios were different from either texture of a single component of imogolite or cellulose microfibrils. The structure of nanocomposite films prepared from respective liquid crystalline phases of the mixtures was investigated by X-ray diffraction analysis and FT-JR. The storage modulus, E', at room temperature was 9.6,11,13,15 GPa for cellulose, 5/5,4/6, and 3/7 nanocomposites films, respectively. The values of E' were insensitive to the temperature above 25℃ for the 5/5 nanocomposite and cellulose films. The 5/5 nanocomposite film was broken at 290℃, while the cellulose film was broken at 250℃. The thermal properties were improved by adding imogolite. On the basis of the results of tunicate/imogolite nanocomposites, a study of bacterial cellulose/imogolite nanocomposites is in progress.