Supramolecular Functionalization of Single-Walled Carbon Nanotubes (SWNTs) with a Photoisomerizable Conjugated Polymer

Abstract

A fluoreneand azobenzene-containing conjugated polymer, poly[2,7-(9,9-didodecylfluorene)-alt-4,4′-azobenzene] (F12AZO) has been successfully synthesized using Suzuki polycondensation. The introduction of two dodecyl chains on the flourene unit resulted in a highly soluble polymer. F12AZO possesses excellent thermal stability, with a decomposition temperature over 400 °C under Ar. The reversible photoisomerization of the azobenzene units was achieved upon alternating photoirradiation with light of wavelength less than 450 nm (cis-form), and light in the range of 450−600 nm (trans-form). The supramolecular complex formation of trans-F12AZO, and cis-F12AZO with single-walled carbon nanotubes (SWNTs) has been studied, and it was found that this polymer can form very strong supramolecular polymer-nanotube assemblies. Furthermore, the trans and cis isomers of F12AZO enable the selective dispersal of individual SWNTs in toluene or THF, and the selectivity of the SWNTs is strongly dependent on the solvent, as well as the type of isomer used. UV−vis−NIR, and photoluminescence−excitation spectroscopy (PLE) were used for the characterization and identification of the nanotube species that are solubilized and exfoliated by this polymer.

Influence of Polymer Electronics on Selective Dispersion of Single‐Walled Carbon Nanotubes

“…Supramolecular polymer‐SWNT complexes of P1 and P2 were prepared with raw HiPCO SWNTs by following previously reported procedures . A few different polymer/SWNT weight ratios were investigated and it was found that a ratio of 1.5:1 polymer/SWNT produced the best dispersions for both P1 and P2 (see the Supporting Information, Figure S4).…”

Ionomer covalent functionalization of single‐walled carbon nanotubes by radical polymerization of zirconium acrylate

“…Unpurified SWCNTs were purified as reported previously by refluxing with nitric acid, followed by subsequent oxidation and annealing, and verified by Raman spectra and TGA. A small amount (50 mg) of unpurified carbon nanotubes was taken in a 100‐mL round bottom flask fitted with condenser, and 60 mL of 3 M nitric acid was added.…”

“…The functionalization of SWCNTs by covalently attaching a polymer is a vital and important method of synthesizing nanomaterials. It is also known that specific polymers interact strongly with nanotube surfaces . The polymer functionalized SWCNT systems are stable and do not decompose or separate during purification, modification, and application .…”

Functionalization of Carbon Nanotubes with Stimuli- Responsive Molecules and Polymers

“…The easy synthesis and controllable photo-switchability of azobenzene have made it a popular building block in the design of photo-responsive CNT dispersants, but one important issue related to it warrants particular attention. It has been noted in some previous studies that when the azobenzene unit is tightly bound to the surface of CNT, the cis-to-trans photoisomerization behavior may vanish due to the quenching effect of CNTs on the excited state of azobenzene [69,70]. It was reported that the effect of photoisomerization in combination with other types of controls (e.g., thermal) [71] could effectively remove the dispersants out of the surface of CNTs.…”