Polyurea-Functionalized Multiwalled Carbon Nanotubes:  Synthesis, Morphology, and Raman Spectroscopy

Abstract

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 chloridefunctionalized MWNTs (MWNT-COCl) by reaction with neat thionyl chloride (SOCl 2 ). MWNT-COCl was reacted with excess 1,6-diaminohexane, affording amino-functionalized MWNTs (MWNT-NH 2 ). In the presence of MWNT-NH 2 , 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 flator 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.

Assembling hyperbranched polymerics

“…Similarly, Gao et al has applied an in situ polycondensation approach to functionalize multiwall carbon nanotubes (MWNTs). 141 The polyurea-coated MWNTs showed interesting self-assembling behavior with flower-like morphologies in the solid state. The growing of hyperbranched polymer by SCVP has been expended on highly curved inorganic surface such as silica nanoparticles and MWNTs.…”

Functionalization and Characterization of MWCNT Produced by Different Methods

“…The amount and type of attached functional groups strongly depends on the type of surface modification applied. Though introducing sufficient amount of oxygen containing functional groups thus improving dispersion of CNTs, chemical modification often leads to significant defects on CNTs surface and cutting [29][30][31][32][33][34][35][36][37][38].…”

Carbon Nanotubes – Imprinted Polymers: Hybrid Materials for Analytical Applications

“…4. Synthesis of CNTs-polymer composites by "Grafting from" approach as reported by Balasubramanian & Burghard, 2005. Many techniques including esterification Sano et al, 2001;Kahn et al, 2002;Huang W. et al, 2003;Lin et al, 2003), "click" chemistry (Li H.M. et al, 2005), layer-bylayer self-assembly (Kong H. et al, 2005;He & Bayachou, 2005;Qin et al, 2005;Artyukhin et al, 2004), pyrene moiety adsorption (Bahun et al, 2006;Martin et al, 2004;Qu et al, 2002;Petrov et al, 2003;Gomez et al, 2003), radical coupling (Liu Y.Q. et al, 2005;Lou et al, 2004), anionic coupling , radical polymerization (Qin et al, 2004a;Shaffer & Koziol, 2002), supercritical CO 2 -solubilized polymerization or coating (Wang J.W.…”

“…et al, 2006), cathodic electrochemical grafting (Petrov et al, 2004) polycondensation (Zeng H.L. et al, 2006a;Gao C. et al, 2005;Nogales et al, 2004), reversible addition fragmentation chain-transfer (RAFT) polymerization (Xu G.Y. et al, 2006;You et al, 2006;Cui H. et al, 2004;Hong et al, 2005Hong et al, , 2006, anionic polymerization (Chen S.M.…”