Department of Materials Science and Engineering, Carnegie Mellon University 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213-3815, United States.
ACS Nano. 2015 Apr 28;9(4):4103-10. doi: 10.1021/acsnano.5b00170. Epub 2015 Mar 24.
Multifunctional polymer nanocomposites that simultaneously possess high modulus and strength, high thermal stability, novel optical responses, and high electrical and thermal conductivity have been actively researched. Carbon nanotubes are considered an ideal additive for composites because of their superlative physical, electronic and optical properties. While nanotubes have successfully added electrical conductivity, thermal stability, and novel optical responses to polymers, mechanical reinforcements, although substantial, have been well below any theoretical estimations. Here, we integrated preformed hydrogels and aerogels of individually dispersed nanotubes with polymer to increase elastic modulus of composites according to Halpin-Tsai model up to at least 25 vol % of nanotubes. Our solution-based fabrication method allowed us to create bulk composites with tunable form-factors, and with polymers that were incompatible with nanotubes. Further, in this approach, nanotubes were not covalently linked among themselves and to the polymer, so intrinsic optical, electrical, and thermal properties of nanotubes could be exploited. The optically active nanotubes, for example, added a strain-dependent, spatially resolved fluorescence to these composites. Finally, the nanoporous nanotube networks suppressed the polymer glass transition and extended the mechanical integrity of polymer well above its polymer melting point, and both the nanotubes and polymer remained thermally stable above their decomposition temperatures.
多功能聚合物纳米复合材料同时具有高模量和强度、高热稳定性、新颖的光学响应以及高导电性，因此受到了广泛的研究。由于碳纳米管具有卓越的物理、电子和光学性能，因此被认为是复合材料的理想添加剂。虽然纳米管已经成功地为聚合物增加了导电性、热稳定性和新颖的光学响应，但机械增强作用虽然很大，但仍远低于任何理论估计。在这里，我们根据 Halpin-Tsai 模型，将预先形成的分散纳米管的水凝胶和气凝胶与聚合物结合，将复合材料的弹性模量提高到至少 25 体积%的纳米管。我们的基于溶液的制造方法允许我们制造具有可调节形状因子的块状复合材料，并且可以使用与纳米管不兼容的聚合物。此外，在这种方法中，纳米管之间以及与聚合物之间没有发生共价键合，因此可以利用纳米管的固有光学、电学和热学性能。例如，具有光学活性的纳米管为这些复合材料增加了应变依赖性的空间分辨荧光。最后，纳米多孔纳米管网络抑制了聚合物的玻璃化转变，并将聚合物的机械完整性扩展到其聚合物熔点以上，并且纳米管和聚合物都在其分解温度以上保持热稳定性。
