Grafting of a hydroxylated poly(ether ether ketone) to the surface of single-walled carbon nanotubes

A hydroxylated poly(ether ether ketone) (HPEEK) derivative has been covalently grafted onto the surface of acid-treated single-walled carbon nanotubes (SWCNTs) following two different esterification approaches. The hydroxylation degree of the HPEEK and the extent of the grafting reactions were determined by thermogravimetric analysis. Microscopic observations revealed an increase in the bundle diameter of the SWCNTs and the heterogeneous composition of the synthesized samples. Infrared, nuclear magnetic resonance and X-ray photoelectron spectra corroborated the grafting success, showing the appearance of signals associated with the ester group. The polymer-grafted SWCNTs display higher decomposition temperatures and a wider range of thermal degradation than the HPEEK. The esterification decreases the crystallization and melting temperature as well as the crystallinity of the HPEEK. The semicrystalline nature of the grafted samples was confirmed by X-ray diffraction analysis, which reveals a diminution in the crystal size of the polymer. Dynamic mechanical studies show an exceptional increase in the storage modulus and glass transition temperature of the polymer by the attachment to the SWCNTs. Slightly better thermal and mechanical properties are observed for the sample with the higher esterification degree. The HPEEK-grafted SWCNTs can be used as fillers to prepare PEEK nanocomposites with enhanced performance.