Department of Fiber and Polymer Technology , KTH Royal Institute of Technology , SE-10044 Stockholm , Sweden.
Department of Materials Science and Engineering , Stanford University , Stanford , California 94305-2205 , United States.
Biomacromolecules. 2019 Feb 11;20(2):598-607. doi: 10.1021/acs.biomac.8b00701. Epub 2018 Aug 17.
A critical aspect in materials design of polymer nanocomposites is the nature of the nanoparticle/polymer interface. The present study investigates the effect of manipulation of the interface between cellulose nanofibrils (CNF) and poly(methyl methacrylate) (PMMA) on the optical, thermal, and mechanical properties of the corresponding nanocomposites. The CNF/PMMA interface is altered with a minimum of changes in material composition so that interface effects can be analyzed. The hydroxyl-rich surface of CNF fibrils is exploited to modify the CNF surface via an epoxide-hydroxyl reaction. CNF/PMMA nanocomposites are then prepared with high CNF content (∼38 wt %) using an approach where a porous CNF mat is impregnated with monomer or polymer. The nanocomposite interface is controlled by either providing PMMA grafts from the modified CNF surface or by solvent-assisted diffusion of PMMA into a CNF network (native and modified). The high content of CNF fibrils of ∼6 nm diameter leads to a strong interface and polymer matrix distribution effects. Moisture uptake and mechanical properties are measured at different relative humidity conditions. The nanocomposites with PMMA molecules grafted to cellulose exhibited much higher optical transparency, thermal stability, and hygro-mechanical properties than the control samples. The present modification and preparation strategies are versatile and may be used for cellulose nanocomposites of other compositions, architectures, properties, and functionalities.
在聚合物纳米复合材料的材料设计中，一个关键的方面是纳米颗粒/聚合物界面的性质。本研究调查了纤维素纳米纤维（CNF）和聚甲基丙烯酸甲酯（PMMA）之间界面的操纵对相应纳米复合材料的光学、热和机械性能的影响。通过最小化材料组成的变化来改变 CNF/PMMA 界面，以便分析界面效应。利用 CNF 纤维丰富的羟基表面，通过环氧化物-羟基反应对 CNF 表面进行改性。然后，通过一种将多孔 CNF 垫用单体或聚合物浸渍的方法，用高 CNF 含量（约 38wt%）制备 CNF/PMMA 纳米复合材料。纳米复合材料界面通过从改性 CNF 表面提供 PMMA 接枝或通过溶剂辅助 PMMA 扩散到 CNF 网络（天然和改性）来控制。直径约为 6nm 的高含量 CNF 纤维导致强界面和聚合物基体分布效应。在不同的相对湿度条件下测量水分吸收和机械性能。与对照样品相比，接枝到纤维素上的 PMMA 分子的纳米复合材料表现出更高的光学透明度、热稳定性和湿机械性能。本研究提出的改性和制备策略具有通用性，可用于具有其他组成、结构、性能和功能的纤维素纳米复合材料。
