The incorporation of functional groups at the end of polyolefin chains offers an opportunity to prepare polyolefin building blocks. The latter can be used to construct polymer architectures based on polyolefins with many desirable properties. For this purpose, the reactivity of the carbon-metal bond formed during a catalytic olefin polymerization process is particularly appealing. The possibility of taking advantage of this reactivity has indeed been enhanced by the discovery of systems in which fast and reversible chain transfer reactions between the active metal center and a main group metal centre are occurring. The recent developments of this catalyzed chain growth (CCG) concept are briefly reviewed. A specific system using a (C 5 Me 5 ) 2 NdCl 2 Li(OEt 2 ) 2 complex in conjunction with nbutyloctylmagnesium is then employed to synthesize an array of end functional polyethylene chains. The potential of these building blocks to build up new macromolecular architectures is discussed.
Carbon nanotube surfaces, activated and randomly decorated with metal nanoclusters, have been studied in uniquely combined theoretical and experimental approaches as prototypes for molecular recognition. The key concept is to shape metallic clusters that donate or accept a fractional charge upon adsorption of a target molecule, and modify the electron transport in the nanotube. The present work focuses on a simple system, carbon nanotubes with gold clusters. The nature of the gold-nanotube interaction is studied using first-principles techniques. The numerical simulations predict the binding and diffusion energies of gold atoms at the tube surface, including realistic atomic models for defects potentially present at the nanotube surface. The atomic structure of the gold nanoclusters and their effect on the intrinsic electronic quantum transport properties of the nanotube are also predicted. Experimentally, multi-wall CNTs are decorated with gold clusters using (1) vacuum evaporation, after activation with an RF oxygen plasma and (2) colloid solution injected into an RF atmospheric plasma; the hybrid systems are accurately characterized using XPS and TEM techniques. The response of gas sensors based on these nano(2)hybrids is quantified for the detection of toxic species like NO(2), CO, C(2)H(5)OH and C(2)H(4).
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