Gao Chao, Jin Yi Zheng, Kong Hao, Whitby Raymond L D, Acquah Steve F A, Chen G Y, Qian Huihong, Hartschuh Achim, Silva S R P, Henley Simon, Fearon Peter, Kroto Harold W, Walton David R M
College of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China.
J Phys Chem B. 2005 Jun 23;109(24):11925-32. doi: 10.1021/jp051642h.
An in situ polycondensation approach was applied to functionalize multiwalled carbon nanotubes (MWNTs), resulting in various linear or hyperbranched polycondensed polymers [e.g., polyureas, polyurethanes, and poly(urea-urethane)-bonded carbon nanotubes]. The quantity of the grafted polymer can be easily controlled by the feed ratio of monomers. As a typical example, the polyurea-functionalized MWNTs were measured and characterized in detail. The oxidized MWNTs (MWNT-COOH) were converted into acyl chloride-functionalized MWNTs (MWNT-COCl) by reaction with neat thionyl chloride (SOCl2). MWNT-COCl was reacted with excess 1,6-diaminohexane, affording amino-functionalized MWNTs (MWNT-NH2). In the presence of MWNT-NH2, the polyurea was covalently coated onto the surfaces of the nanotube by in situ polycondensation of diisocyanate [e.g., 4,4'-methylenebis(phenylisocyanate)] and 1,6-diaminohexane, followed by the removal of free polymer via repeated filtering and solvent washing. The coated polyurea content can be controlled to some extent by adjusting the feed ratio of the isocyanato and amino groups. The structure and morphology of the resulting nanocomposites were characterized by FTIR, NMR, Raman, confocal Raman, TEM, EDS, and SEM measurements. The polyurea-coated MWNTs showed interesting self-assembled flat- or flowerlike morphologies in the solid state. The signals corresponding to that of the D and G bands of the carbon nanotubes were strongly attenuated after polyurea was chemically tethered to the MWNT surfaces. Comparative experiments showed that the grafted polymer species and structures have a strong effect on the Raman signals of polymer-functionalized MWNTs.
采用原位缩聚方法对多壁碳纳米管（MWNTs）进行功能化处理，得到了各种线性或超支化缩聚聚合物[如聚脲、聚氨酯以及聚（脲-聚氨酯）键合碳纳米管]。接枝聚合物的量可通过单体的进料比轻松控制。作为一个典型例子，对聚脲功能化的MWNTs进行了详细的测量和表征。通过与纯亚硫酰氯（SOCl₂）反应，将氧化的MWNTs（MWNT-COOH）转化为酰氯功能化的MWNTs（MWNT-COCl）。MWNT-COCl与过量的1,6-二氨基己烷反应，得到氨基功能化的MWNTs（MWNT-NH₂）。在MWNT-NH₂存在的情况下，通过二异氰酸酯[如4,4'-亚甲基双（苯基异氰酸酯）]和1,6-二氨基己烷的原位缩聚反应，将聚脲共价包覆在纳米管表面，然后通过反复过滤和溶剂洗涤除去游离聚合物。通过调节异氰酸酯基和氨基的进料比，可以在一定程度上控制包覆的聚脲含量。通过傅里叶变换红外光谱（FTIR）、核磁共振（NMR）、拉曼光谱、共聚焦拉曼光谱、透射电子显微镜（TEM）、能谱分析（EDS）和扫描电子显微镜（SEM）测量对所得纳米复合材料的结构和形态进行了表征。聚脲包覆的MWNTs在固态下呈现出有趣的自组装平面或花状形态。在聚脲化学连接到MWNT表面后，与碳纳米管的D带和G带相对应的信号被强烈衰减。对比实验表明，接枝聚合物的种类和结构对聚合物功能化MWNTs的拉曼信号有很强的影响。
