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Multi-walled carbon nanotubes (MWNTs) are placed under atomic nitrogen flow formed through an Ar + N 2 microwave plasma in order to functionalize covalently their side walls with nitrogen-containing groups. The MWNT surface analyzed by X-ray photoelectron spectroscopy shows the presence of amides, oximes and mainly amine and nitrile functions grafted in this way. In order to highlight the actual location of the amine functions grafted on MWNTs, they were considered as initiation species in ring-opening polymerization of e-caprolactone using triethylaluminium as activator. The so-generated poly(e-caprolactone) chains remain grafted on the MWNTs via amide bonds and form polyester islets along the nanotubes surface. TEM images of these MWNT surfaces grafted with poly(e-caprolactone) show a good amino-sidewall distribution. This work demonstrates the side-wall amino-functionalization of carbon nanotubes readily achieved by microwave plasma with the possibility to reach within a short time period very high contents in nitrogen-based functions (y10 at.%).

Dc and ac conductivities in a broad angular frequency, 2π Â 10 À3 s À1 < ω < 2π Â 10 7 s À1 , and temperature range, 133 K < T < 323 K, were measured in poly(εcaprolactone)/multiwalled carbon nanotube nanocomposites as a function of weight concentration (0 wt % e p e 3 wt %) . The universal dynamic response was observed at low p values, and the parameters were adjusted by working in several domains. Scaling laws predicted by the variation of dc conductivity as a function of p or characteristic frequency in percolation theory were followed and showed the formation of a 3D percolative cluster at concentration values as low as 0.3 wt %. The existence of tunneling conduction was proved, and its independence on temperature indicates that we are in the presence of a conventional tunnel effect among nanoparticles not yet in physical contact, through energy barriers made by the polymer chains. All these combined facts allowed construction of a master curve evidencing the timeÀtemperatureÀcomposition superposition existing in the poly(ε-caprolactone)/multiwalled carbon nanotube nanocomposites studied here.

International audienceVertically aligned multiwalled carbon nanotubes (v-MWCNTs) are functionalized using atomic oxygen generated in a microwave plasma. X-ray photoelectron spectroscopy depth profile analysis shows that the plasma treatment effectively grafts oxygen exclusively at the v-MWCNT tips. Electron microscopy shows that neither the vertical alignment nor the structure of v-MWCNTs were affected by the plasma treatment. Density functional calculations suggest assignment of XPS C 1s peaks at 286.6 and 287.5 eV, to epoxy and carbonyl functional groups, respectively