Functionalization of Carbon Nanotubes via Electrophilic Substitution Reaction in Polyphosphoric Acid

Abstract

Various 4-substituted benzoic acids were introduced onto the surface of MWNTs. Depending upon the electron-donating or electron-withdrawing nature of substituents to the 4-position of carboxylic acid, the amount of substituents onto MWNTs varied from 4-40 wt%. The stronger electron-donating nature, the compound displayed the better reactivity. Some of them were used as an additive to polymer nanocomposites. For example, as-received MWNT, 4-ethoxybenzoic acid (EBA) and 4-methoxybenzoic acid (MBA) functionalized MWNTs were dispersed in ethylene glycol (EG). Because of the structural similarity, the mixture of EBA-MWNT (0.4 wt%) and EG displayed the best dispersion. In-Situ polycondensation of EG and terephthalic acid (TPA) in the presence of pristine MWNT, MBA-MWNT, or EBA-MWNT were carried out and compared the images from SEM taken at the same magnification for these nanocomposites, it is clear that EBA-MWNT in PET matrix is most homogeneously dispersed and the interfacial boundary between EBA-MWNT and PET matrix is practically non-discernable.