Fabien Monteverde

Functionalization of carbon nanotubes by atomic nitrogen formed in a microwave plasma Ar + N2 and subsequent poly(ε-caprolactone) grafting

Multi-walled carbon nanotubes (MWNTs) are placed under atomic nitrogen flow formed through an Ar + N2 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 (∼10 at.%).

Supported coordination polymerization: a unique way to potent polyolefin carbon nanotube nanocomposites

Homogeneous surface coating of long carbon nanotubes is achieved by in situ polymerization of ethylene as catalyzed directly from the nanotube surface-treated by a highly active metallocene-based complex and allows for the break-up of the native nanotube bundles leading, upon further melt blending with HDPE, to high-performance polyolefinic nanocomposites.

Supported metallocene catalysis as an efficient tool for the preparation of polyethylene/carbon nanotube nanocomposites: effect of the catalytic system on the coating morphology

Homogeneous or periodical surface coating of multiwalled carbon nanotubes (MWNTs) can be achieved by in situ polymerization of ethylene as catalyzed directly from the nanotube surface- treated by a highly active metallocene-based complex, e.g., Cp*2ZrCl2/methylaluminoxane. This polyethylene (PE) coating allows for the break-up of the native nanotube bundles. Immobilization of methylaluminoxane onto the surface of the carbon nanotubes was evidenced by scanning electron microscopy (SEM) and confirmed by X-ray photoelectron microscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The thermal behaviour and degradation were studied by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Transmission electron microscopy (TEM) was used to image polymer-coated MWNTs, showing either a relatively smooth or a textured polymer coating present on the surface of individual, debundled nanotubes, i.e., PE/MWNT nanohybrid “sausage”-like or “shish-kebab”-like structures, respectively. It was clearly demonstrated that by modifying the design of the catalytic complexes, it was possible to tune by a reproducible way the morphology of the PE coating around the MWNTs.

Microscopic Morphology of Chlorinated Polyethylene-Based Nanocomposites Synthesized from Poly(ε-caprolactone)/Clay Masterbatches

Chlorinated polyethylene (CPE) nanocomposites were synthesized by melt blending clay-rich/poly(epsilon-caprolactone) (PCL) masterbatches to CPE matrices. The masterbatches were prepared following two synthetic routes: either PCL is melt-blended to the clay or it is grafted to the clay platelets by in situ polymerization. The microscopic morphology of the nanocomposites was characterized by X-ray diffraction, atomic force microscopy, transmission electron microscopy, and modulated temperature differential scanning calorimetry. When using free PCL, intercalated composites are formed, with clay aggregates that can have micrometric dimensions and a morphology similar to that of the talc particles used as fillers in commercial CPE. PCL crystallizes as long lamellae dispersed in the polymer matrix. When using grafted PCL, the nanocomposite is intercalated/exfoliated, and the clay stacks are small and homogeneously dispersed. PCL crystallizes as lamellae and smaller crystals, which are localized along the clay layers. Thanks to the grafting of PCL to the clay platelets, these crystalline domains are thought to form a network with the clay sheets, which is responsible for the large improvement of the mechanical properties of these materials.

Structuration of Semiconducting Polymer Thin Films by Nanorubbing

In this paper, we study the behavior of thin films of a semiconducting polymer, poly(3-hexylthiophene)-P3HT under the application of a physical constraint. We have rubbed P3HT thin films with a velvet cloth, which leads to the alignment of the polymer chains along the sliding direction at the film surface. Annealing the rubbed films up to the crystallization temperature, leads to the propagation of the surface orientation to the whole film. In order to gain spatial and geometrical control on the rubbing process, we have used nano-rubbing. Using the stylus of an AFM working in contact mode, the nano-rubbing process can be performed locally on an area of defined size. These chain-aligned structures can be permanent thanks to the crystallization process. This study opens interesting opportunities to control the molecular order within the channel of field-effect transistors