In-situ grafting of hyperbranched poly(ether ketone)s onto multiwalled carbon nanotubes via the A3+B2 approach

Trimesic acid and phenyl ether were in-situ polymerized as A(3) and B-2 monomers, respectively, in the presence of a fixed amount (10 wt %) of multiwalled carbon nanotube (MWNT) to afford hyperbranched poly(ether ketone)s (PEK's)/MWNT nanocomposites. The feed ratios of A(3) and B-2 monomers vary from 3:2 to 1:2 in the A(3) + B-2 polycondensations. The polymerization was carried out in a mildly acidic medium, i.e., poly(phosphoric acid) or PPA, with an optimized amount of phosphorus pentoxide (P2O5) added. The overall evidence based on the data of elemental analysis (EA), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) implicates that hyperbranched PEK's were attached to the surface of MWNT to form hyperbranched PEK-g-MWNT nanocomposites. Furthermore, MWNT remained structurally intact under the polymerization and workup conditions. Evidently driven by the molecular architecture of globular hyperbranched polymers, the morphology of the nanocomposites resembles "mushroom-like clusters on MWNT stalks". The hyperbranched PEK-g-MWNT nanocomposites were soluble in polar aprotic solvents stemming from numerous carboxylic acids on their surfaces. When some of samples were dispersed in 1 M LiOH aqueous solutions, they formed very stable suspensions. The resulting lithiated nanocomposites are being investigated in the applications such as ion conductivity and energy capacitance.