Noncovalent Surface Functionalization of Multi-walled Carbon Nanotubes with Polyhedral Oligomeric Silsesquioxane Nanoparticles Based on CH-π Interactions

One-pot chain walking copolymerization of ethylene and polyhedral oligomeric silsesquioxane (POSS) monomer was first performed at 0.1 MPa/35 degrees C with a Pd-diimine catalyst to synthesize hyperbranched polyethylene covalently tethered with multiple POSS nanoparticles (HBPE @ POSS). The resulting HBPE@ POSS was then used to functionalize multi-walled carbon nanotubes (MWCNTs) under the assistance of ultrasonication in tetrahydrofuran (THF) and chloroform, respectively. The structure and POSS portion of the HBPE @ POSS were characterized via proton nuclear magnetic resonance (H-1-NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and wide-angled X-ray diffraction (WAXD) techniques, respectively. Further, the dispersibility, morphology and aggregate state of HBPE @ POSS functionalized MWCNTs, and noncovant interactions between MWCNTs and HBPE @ POSS as well, are investigated through UV-Vis absorbance spectroscopy, transmittance electron microscopy (TEM), WAXD, Fourier-transformed infrared (FTIR) spectroscopy and TGA techniques, respectively. It is testified that POSS can be covalently introduced into hyperbranched polyethylene with a portion of 39.0 wt% in the HBPE @ POSS. The HBPE@ POSS is found to effectively debundle/solubilize MWCNTs both in THF and chloroform, giving stable MWCNTs solutions with concentrations up to 987 mg/L in THF and 511 mg/L in chloroform. Also, it is found that PUSS of certain portion can be irreversibly adsorbed onto MWCNTs by means of the noncovalent CH-pi interactions between MWCNTs and HBPE @ POSS. It is expected that more inorganic nanoparticles (INPs) can be introduced onto CNTs through this method, thus leading to a novel strategy for surface functionalization of CNTs with INPs.