Arenas-García Josué, Escárcega-Bobadilla Martha V, Zelada-Guillén Gustavo A
Department of Analytical Chemistry, School of Chemistry, National Autonomous University of Mexico.
Department of Organic Chemistry, School of Chemistry, National Autonomous University of Mexico;
J Vis Exp. 2018 Apr 1(134):56267. doi: 10.3791/56267.
We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.
我们展示了一种简单的方案，通过自由基聚合策略在原始多壁碳纳米管（MWCNT）的侧壁上接枝聚苯乙烯（PS）链，以实现对纳米管表面性质的调控，并产生纳米结构的超分子自组装。首先，通过双相催化介导的氧化反应对原始纳米管进行选择性羟基化，在侧壁上产生表面分布的反应位点。随后，使用硅烷化的甲基丙烯酸前体用甲基丙烯酸部分修饰后者的反应位点，以产生可聚合位点。这些可聚合基团可以引发苯乙烯的进一步聚合，以制备一种杂化纳米材料，其中PS链接枝到纳米管侧壁上。通过热重分析（TGA）确定并量化聚合物接枝含量、引入的硅烷化甲基丙烯酸部分的量以及纳米管的羟基化修饰。通过傅里叶变换红外光谱（FT-IR）确认反应性官能团羟基和硅烷化甲基丙烯酸酯的存在。当通过透射电子显微镜（TEM）分析浇铸样品时，四氢呋喃（THF）中的聚苯乙烯接枝碳纳米管溶液提供壁对壁共线自组装的纳米管。当从含有未接枝对应物的类似溶液中类似地浇铸合适的空白样品时，不会获得这些自组装。因此，该方法能够修饰纳米管侧壁上的各向异性斑点，从而导致在纳米尺度上的自发自组织。
