摘要/Abstract
单壁碳纳米管（SWNTs）的分散性是影响其走向大规模应用的一个重要因素.尤其为满足未来绿色化学的要求，制备环保、稳定、均匀分散的单壁碳纳米管水溶液尤为重要.基于此，我们利用一种水溶性的共轭聚电解质聚（3-甲基咪唑盐己基噻吩）（P3MHT），来分散单壁碳纳米管.通过紫外-可见光谱仪、荧光光谱仪、透射电子显微镜、纳米粒度-Zeta电位分析仪、热重分析仪等仪器对制备的聚噻吩/碳纳米管复合物进行表征，结果表明聚噻吩主链与碳纳米管通过π-π相互作用形成电荷转移复合物，聚噻吩侧链上的离子基团则赋予复合物良好的水溶性，从而均匀分散碳纳米管.与常用于分散碳纳米管的小分子表面活性剂十二烷基硫酸钠相比，相同质量的P3MHT可明显提高碳纳米管在水相中的溶度和均匀分散性.该复合物溶液具有非常高的稳定性，在静置6个月后复合物分散性基本保持不变.
关键词: 共轭聚电解质, 单壁碳纳米管, 水溶液分散, 稳定性
The dispersion of single-walled carbon nanotubes (SWNTs) is a key point to develop their extensive applications. Especially, to meet the requirements of future green chemistry, the preparation of environmentally-friendly, highly stable and well-distributed SWNTs in aqueous solution becomes particularly important. Based on it, a water-soluble conjugated polyelectrolyte, namely poly[3-[6-(N-methylimidazolium)hexyl]thiophene] (P3MHT) was designed and used to disperse SWNTs through non-covalent strategy. P3MHT was synthesized by a modified Grignard metathesis (GRIM) polymerization followed by quaternization of the bromohexyl side groups of the poly[3-(6-bromohexyl)thiophene] with N-methylimidazole. The P3MHT/SWNTs nanocomposites were prepared by mixing P3MHT and SWNTs in water during ultrasonication followed by centrifugation. UV-vis absorption spectroscopy, photoluminescence (PL) spectroscopy, transmission electron microscope (TEM), Zeta-nano electric potential analyzer, thermogravimetric (TGA) analysis were applied to characterize P3MHT/SWNTs nanocomposites. Compared to the commercial sodium dodecyl sulfate (SDS) surfactant to disperse SWNTs in aqueous solution, P3MHT exhibited a much better ability to disperse SWNTs under the same condition, i.e., the concentration of SWNTs dispersed by P3MHT was about two times than that of SWNTs dispersed by SDS. In P3MHT/SWNTs nanocomposite solution, SWNTs were exfoliated to form individuals or small bundles with an average size of 298 nm. However, in SDS/SWNTs solution, SWNTs preferred to form small aggregates with an average size of more than 500 nm. The P3MHT backbones were wrapped around individual SWNTs via π-π interactions to form the charge-transfer complexes. The ionic side chains of P3MHT not only made the nanocomposites dispersed in water, but also prevented the aggregation of SWNTs by electrostatic repulsion, resulting in aqueous dispersion of P3MHT/SWNTs nanocomposites. While SDS molecules were adsorbed on the surface of SWNTs via hydrophobic alkyl chains, which was much weaker than the π-π interactions between P3MHT and SWNTs. Such P3MHT/SWNTs nanocomposite solution exhibited high stability which remained almost unchanged after 6 months while SDS/SWNTs nanocomposite had already precipitated then. Overall, it provides a promising and simple method to develop highly stable and water processed SWNTs.
Key words: conjugated polyelectrolytes, single-walled carbon nanotubes (SWNTs), aqueous dispersion, stability
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