In situ chemical oxidative graft polymerization of thiophene derivatives from multi-walled carbon nanotubes

Abstract

We describe an effective route for the in situ chemical oxidative graft polymerization of thiophene derivatives from multi-walled carbon nanotubes (MWCNTs). To this goal, MWCNTs was carboxylated (MWCNTs-COOH) by conventional acid oxidation process, and then carboxylic groups were converted to acylchloride groups (MWCNTs-COCl) by treating of MWCNTs-COOH with thionyl chlorides. These acylchloride-functionalized MWCNTs were further reacted with 2-hydroxymethylthiophene (HMT) to produce thiophene-functionalized multi-walled carbon nanotubes (MWCNTs-T). Afterwards, the graft polymerization of 2,2'-bithiophene (BT), 3,4-ethylenedioxythiophene (EDOT), and 3-dodecylthiophene (DDT) monomers from MWCNTs-T was initiated by oxidized thiophene groups in the MWCNTs after addition of ferric chloride (FeCl3), an oxidative catalyst for polythiophene derivatives synthesis, and FeCl3-doped PBT, PEDOT, and PDDT was chemically grafted to the MWCNTs by oxidation polymerization. The chemical structures of all samples as representatives were characterized by Fourier transform infrared (FTIR) spectroscopy. The thermal properties of the MWCNTs-g-polythiophenes and their pure polymers were examined by thermogravimetric analysis (TGA). Moreover, direct and clear evidence of the PBT, PEDOT, and PDDT chemically grafted to the MWCNTs were obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).