Philippe Dubois tells Journal of Materials Chemistry about his hot paper.

1. Can you briefly describe what you achieved in this article?
We have developed an efficient process allowing the homogeneous or periodical surface coating of multiwalled carbon nanotubes (MWNTs) 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. The material obtained was extensively characterized, in particular by transmission electron microscopy (TEM) used to image polymer-coated MWNTs, showing either relatively smooth or 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.

2. Could you explain the significance of your article to the non-specialist? 
Homogeneously dispersing rigid particles in polymer matrices represents a very common and widely used method that allows for readily increasing the stiffness of the so-obtained composite materials. Depending on the intrinsic nature of the added filler, other properties can also be enhanced such as fire resistance, electrical, and thermal properties. Among the tremendous number of nanomaterials, carbon nanotubes are one of the most used nanofillers. However, the key challenge remains reaching a high level of nanotube dissociation, ultimately leading to their fine individual dispersion upon melt blending within the selected polymer matrix. What we have discovered is an efficient process, so-called polymerization filling-technique (PFT), that allows the in situ  polymerization of olefinic monomers as catalyzed directly from the nanofiller surface and subsequent nanotube coating by the precipitated and crystallized polyolefin chains.  As a result, complete destructuration of the native carbon nanotube aggregates is achieved upon melt blending with usual polymer matrices leading finally to nanocomposites exhibiting improved properties when compared with the unfilled polymers or conventional microcomposites.

3. What has motivated you to conduct this work? 
We are mainly interested in developing fundamental knowledge in order to be able to elaborate new melt processable nanophase-separated hybrid materials with controlled architecture, derived from low cost petrochemical olefin feedstocks without sacrificing easy polymer melt processing. In contrast to the most current nanocomposites, where mainly physical bonding between nanofiller and matrix are obtained, this research strives for combining chemical and physical bonding which would allow a real breakthrough in materials properties. Interestingly, this research has been conducted in close collaboration with Nanocyl (Belgium) in the frame of the Nanohybrid project (STREP NMP3-CT-2005-516972) of the 6th EU Framework Program.

4. Where do you see this work developing in the future? 
Surface modification of carbon nanotubes allowing for their de-aggregation and fine dispersion within the selected polymer matrix  paves the way to larger scale production of masterbatches, actually highly filled in carbon nanotubes, and readily usable in various industrial applications such as materials design for automotive parts, packaging, and any types of advanced functional and high performance materials. 

5. Are there any particular challenges facing future research in this area? 
One of the challenges is to upgrade and diversify the polyolefin compositions produced by transition metal catalyzed polymerizations. The production of polyolefin materials offers at the same time economical, environmental, and application-oriented advantages.

Professor Philippe Dubois

Philippe Dubois graduated in Chemistry from the Facultés Universitaires Notre-Dame de la Paix (FUNDP, Namur, Belgium) in 1987. He received his PhD degree in Chemistry from University of Liège (ULg) in 1991. The same year, he worked as a postdoc fellow for Dow Chemical (Terneuzen, Holland) and the Laboratory of Macromolecular Chemistry and Organic Catalysis directed by Prof. P. Teyssié at ULg. Then he joined the National Fund for Scientific Research (FNRS) at ULg till 1997. In 1994, he worked as visiting scientist at the Chemical Research Engineering Department of the Michigan State University (MSU). In 1997, he moved to University of Mons-Hainaut (UMH) where he obtained the chair of macromolecular chemistry and created/directed the Laboratory of Polymeric and Composite Materials (now ca. 35 people). He has co-authored over 300 publications in international journals, 160 personal communications at conferences and is co-inventor of 37 patents. He co-edited 5 books. He is full professor at UMH, adj. professor at ULg and invited professor at FUNDP, MSU, and Faculté Polytechnique de Mons (FPMs). He is Scientific Director at Materia Nova Research Center in Mons.  In 2003 he became president of the Institute of Chemistry at UMH. Very recently, he co-founded the Center of Innovation and Research in Materials & Polymers (CIRMAP, with ca. 80 members).  He is currently director of CIRMAP and President of the Belgian Royal Chemical Society.