Carbon nanotubes functionalization with sulfonated poly (ether ether ketone) chains

Among many extraordinary properties, CNTs have a very high Young modulus, generally reported with a value of ~ 1 TPa, making this kind of material even stronger than diamond and carbon fiber. Moreover their very light weight makes them first choice materials for mechanical reinforcement of polymer matrices. Most of previous studies using CNTs deal with so-called physical mixing, meaning that there is no strong link between polymer and nanotube surface, resulting in a relatively poor enhancement of the composite Young's modulus. In our study, we first investigated the functionalization of multi-walled carbon nanotubes (MWNTs) surface by sulfonated poly (ether ether ketone) SPEEK chains using a direct attachment reaction, PEEK being known as a very promising polymer especially in aerospace field for its particularly high glass transition and melting temperature, compared with most of polymer material.[1] MWNTs were oxidized by a nitric acid treatment to generate carboxyl groups on their surface, which then react with sulfonated groups of SPEEK using hexane diamine as an interlinking molecule.[2,3] Evidence of covalent functionalization of MWNTs by SPEEK macromolecules was given by near-edge X-ray absorption fine structure spectroscopy (NEXAFS) at the C K-edge, O K-edge, and N K-edge and X-ray photoelectron spectroscopy (XPS). Mechanical properties of the MWNT-SPEEK composite material were then tested to quantify the enhancement of Young's modulus.