627 Full Paper Macromolecular Chemistry and Physics wileyonlinelibrary.com DOI: 10.1002/macp.201100659 Ethylene- co-Norbornene Copolymers Grafted Carbon Nanotube Composites by In Situ Polymerization Laura Boggioni,* Giulia Scalcione, Andrea Ravasio, Fabio Bertini, Cristina D’Arrigo, Incoronata Tritto Vinyl functionalized multiwalled carbon nanotubes (MWCNT-vinyl) are synthesized and used as monomers to prepare poly(ethylene- co-norbornene)-grafted carbon nanotube composites by in situ polymerization with [Ti( η 5 -C 5 Me 5 )(N=C t Bu 2 )Cl 2 ] activated with methylalumoxane (MAO). The glass transition temperatures ( T g ) of grafted MWCNT composites are more than 30 °C higher than those of copolymers. This difference is rationalized by the immobilization of the copolymer chain to the MWCNT surface by a covalent bond. The Young’s mod- ulus is shown to increase by more than 200% compared to poly(ethylene- co-norbornene) by incorporating 3.4 wt% func- tionalized MWCNT. L. Boggioni, G. Scalcione, A. Ravasio, F. Bertini, I. Tritto Istituto per lo Studio delle Macromolecole, Consiglio Nazionale delle Ricerche, via E. Bassini 15, 20133 Milano, Italy E-mail: boggioni@ismac.cnr.it C. D’Arrigo Istituto per lo Studio delle Macromolecole, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy blending methods generally used for preparing nano- composites are not suitable for polyolefins. [4] The in situ polymerization of monomers in the presence of nanopar- ticles and CNT is a promising method for obtaining nano- composites in which nanotubes are dispersed individually at nanometer level. [5–7] Copolymers of ethylene (E) with norbornene (N) [P(E- co-N)] are thermoplastic materials that have recently received great attention because of their attractive properties [8,9] such as high T g , high optical transparency, excellent moisture barrier, and chemical resistance. These distinctive properties enable them to be utilized for a wide variety of uses in advanced packaging, engineering components, and optical applications. Among the in situ methodologies hitherto reported, P(E- co-N)-MWCNT were obtained with MAO-activated metallocenes by polymerization filling technique (PFT), [6] and more recently by in situ synthesis with a highly active methylalumoxane (MAO) free catalytic system. [9] Another method involves in situ polymerization in the presence of functionalized nanotubes which can be inserted into the polymer chain, resulting in covalent attachment of nanotubes to the polymer. Consequently, better dispersion and formation of a strong interface between nanotubes and polymer matrix are achieved. 1. Introduction The carbon nanotubes (CNT) are endowed with inter- esting properties that modify the characteristics of the polymer matrix in which they are embedded. [1–4] The blending of polymer matrices with well dispersed CNT as the filler (in low concentration, less than 5 wt%) may enhance and modify the mechanical, electric, dielectric, thermal, and crystallization properties of the host mate- rial or even induce new nanoeffects. Such enhancement and thus the success of a nanocomposite is related to the achievement of a good dispersion of the nanofiller in the polymer matrix. This is hindered by the tendency of CNT to agglomerate in bundles due to van der Waals interac- tions. Several approaches have been used to overcome such difficulty and to enhance chemical compatibility between CNT and polymer chains. Solution and melt Ti N Cl Cl O O O O O O t Bu t Bu i) toluene, TIBA ii) ultrasounds iii) + MAO O O 3 3 3 3 Macromol. Chem. Phys. 2012, 213, 627−634 © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim