Khan Mohammad Zahidul H, Alrawashdeh Ahmad I, Aljohani Suad, Zhao Yuming, Lagowski Jolanta B
Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, NL A1B 3X7, Canada.
Phys Chem Chem Phys. 2017 Oct 25;19(41):28071-28082. doi: 10.1039/c7cp04851c.
π-Conjugated oligomers with relatively short molecular backbones can be used effectively in dispersion of carbon nanotubes (CNTs). In this paper, we present a systematic study on interactions between diphenylene-fluorene oligomers (DPFs) and single-walled CNTs (SWCNTs) using density functional theory (DFT) calculations. Four DFT methods are used in this work: the long range (LR)-corrected CAM-B3LYP, the dispersion (D)-corrected B97D, the LR- and D-corrected wB97XD, and the hybrid B3LYP. The DPFs examined in this study contain different functional groups attached to the π-conjugated backbone, including two different end groups, carboxaldehyde (ALD) and dithiafulvenyl (DTF), and three different side chains (SCs), CH, OCH, and SCH. The computational results disclose the effects of end groups, SCs, and DFT methods on structures, dipole moments, and energetics of isolated DPFs and DPF/SWCNT combinations. Consistent with our previous study (involving oligo(p-phenylene ethynylene)s (OPEs)) [Aljohani et al., J. Phys. Chem. C, 2017, 121, 4692-4702], our results herein demonstrate that the type of end group plays a key role in determining the strength of interactions between SWNTs and conjugated oligomers. In particular, DTF-endcapped oligomers have a stronger electrostatic interaction with SWCNT than ALD-endcapped oligomers do. As a result, DTF-endcapped conjugated oligomers become more polarized than ALD-endcapped oligomers after complexing with SWCNTs. The magnitude of binding energy, on the other hand, shows dependence on the orientation of the backbone and side chains of these oligomers relative to the SWCNT which in the case of fluorene-based oligomers is not always favourable for optimal binding. This study indicates that fluorene-based oligomers might not be as good dispersants of SWCNTs as OPEs.
具有相对较短分子主链的π共轭低聚物可有效地用于碳纳米管（CNT）的分散。在本文中，我们使用密度泛函理论（DFT）计算对二亚苯基芴低聚物（DPF）与单壁碳纳米管（SWCNT）之间的相互作用进行了系统研究。本工作使用了四种DFT方法：长程（LR）校正的CAM-B3LYP、色散（D）校正的B97D、LR和D校正的wB97XD以及杂化B3LYP。本研究中考察的DPF包含连接到π共轭主链上的不同官能团，包括两个不同的端基，即醛基（ALD）和二硫富烯基（DTF），以及三个不同的侧链（SC），即CH、OCH和SCH。计算结果揭示了端基、侧链和DFT方法对孤立的DPF以及DPF/SWCNT组合的结构、偶极矩和能量学的影响。与我们之前的研究（涉及聚对苯撑乙炔（OPE））[Aljohani等人，《物理化学杂志C》，2017年，121卷，4692 - 4702页]一致，我们在此的结果表明端基类型在决定SWNT与共轭低聚物之间相互作用的强度方面起着关键作用。特别是，DTF封端的低聚物与SWCNT的静电相互作用比ALD封端的低聚物更强。因此，与SWCNT络合后，DTF封端的共轭低聚物比ALD封端的低聚物极化程度更高。另一方面，结合能的大小显示出依赖于这些低聚物的主链和侧链相对于SWCNT的取向，而在芴基低聚物的情况下，这并不总是有利于实现最佳结合。本研究表明芴基低聚物作为SWCNT的分散剂可能不如OPE。
