Department of Biomaterial Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Nanoscale. 2014 Jan 7;6(1):392-9. doi: 10.1039/c3nr04102f. Epub 2013 Nov 8.
A highly tough and transparent film material was prepared from synthetic saponite (SPN) nanoplatelets of low aspect ratios and nanofibrillar cellulose. The nanofibrillar cellulose was chemically modified by topological surface oxidation using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a catalyst. Both synthetic SPN nanoplatelets and TEMPO-oxidized cellulose nanofibrils (TOCNs) have abundant negative charges in high densities on their surfaces and are dispersed in water at the individual nanoelement level. Layered nanocomposite structures of the SPN nanoplatelets and TOCNs were formed through a simple cast-drying process of the mixed aqueous dispersions. The TOCN/SPN composites with 0-50% w/w SPN content were optically transparent. Mechanical properties of the TOCN/SPN composites varied depending on the SPN content. The composite with 10% w/w SPN content (5.6% volume fraction) exhibited characteristic mechanical properties: Young's modulus of 14 GPa, tensile strength of 420 MPa, and strain-to-failure of 10%. The work of fracture of the composites increased from 4 to 30 MJ m(-3)- or by more than 700%--as the SPN content was increased from 0 to 10% w/w. This surprising improvement in toughness was interpreted based on a model for fracture of polymer composites reinforced with low-aspect-ratio platelets.
一种具有高韧性和高透明度的薄膜材料是由低纵横比的合成皂石（SPN）纳米片和纳米纤维纤维素制备的。纳米纤维纤维素通过使用 2,2,6,6-四甲基哌啶-1-氧基（TEMPO）作为催化剂的拓扑表面氧化进行化学修饰。合成 SPN 纳米片和 TEMPO 氧化的纤维素纳米纤维（TOCN）在其表面上具有高密度的丰富负电荷，并在水中以单个纳米元件的水平分散。通过混合水基分散体的简单浇铸干燥工艺形成 SPN 纳米片和 TOCN 的层状纳米复合材料结构。含有 0-50% w/w SPN 含量的 TOCN/SPN 复合材料具有光学透明性。TOCN/SPN 复合材料的机械性能取决于 SPN 含量。含有 10% w/w SPN 含量（5.6%体积分数）的复合材料表现出特征机械性能：杨氏模量为 14 GPa，拉伸强度为 420 MPa，断裂应变为 10%。随着 SPN 含量从 0 增加到 10% w/w，复合材料的断裂功从 4 增加到 30 MJ m(-3)，或增加了 700%以上。这种韧性的惊人提高可以根据用于增强低纵横比片状物的聚合物复合材料的断裂模型来解释。
