非离子表面活性剂对多壁碳纳米管在乙醇中高浓度分散的作用

如果能在无需聚合物或共价官能团辅助的条件下, 将多壁碳纳米管(MWNTs)高浓度地分散在乙醇中, 那么向各种复合材料引入MWNTs的过程就会更加便捷. 为此, 制备了多种含有表面活性剂的多壁碳纳米管乙醇悬浮液并对比考查了它们的稳定性. 非离子表面活性剂Triton X-100 和Tween 65显示出了在乙醇中分散悬浮高浓度MWNTs的能力, 能够使1.0 g·L-1 MWNTs乙醇悬浮液的上层清液经240 h后浓度仍分别在0.50和0.35 g·L-1以上. 这样长时间稳定的、没有聚合物或共价官能团辅助的MWNTs乙醇悬浮液, 其浓度比文献报道的值高. 进一步探讨了这些非离子表面活性剂分子结构对于分散MWNTs的优势, 并直观给出了其吸附于碳纳米管表面的可能形式. X射线光电子能谱和透射电子显微镜的表征结果都证实了表面活性剂分子吸附于碳纳米管表面.

Effect of Non-Ionic Surfactants on the Dispersion of Multiwalled Carbon Nanotubes at High Loading in Ethanol

The dispersion of highly concentrated multiwalled carbon nanotubes (MWNTs) in ethanol without polymer or covalent functionalization would generally facilitate the addition of MWNTs to a wide range of composite materials. To this end, suspensions of MWNTs in ethanol with various surfactants were prepared and their stabilities were evaluated. Non-ionic surfactants such as Triton X-100 and Tween 65 could suspend high-loading nanotubes in ethanol. MWNT suspensions in ethanol with Triton X-100 and Tween 65 initial supernatant concentrations of 1.0 g·L-1 were prepared and their concentrations were more than 0.50 and 0.35 g·L-1 after 240 h, respectively. These concentrations for MWNT suspensions, which are stable over the long term in ethanol without polymer or covalent functionalization, are higher than others reported in literature. The structural advantage of these non-ionic surfactant molecules for MWNT dispersion is discussed and a schematic representation is given to illustrate their adsorption on nanotube surfaces. The existence of surfactant molecules adsorbed on the nanotube surfaces was confirmed by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy(TEM).