Carbon Nanotubes as a Ligand in Cp 2 ZrCl 2 -Based Ethylene Polymerization Sungjin Park,* 1 Seung Woong Yoon, 1 Kyung-Bok Lee, 1 Dong Jin Kim, 1 Young Hwan Jung, 1 Youngkyu Do, 1 Hyun-jong Paik, 2 Insung S. Choi* 1 1 Department of Chemistry and School of Molecular Science (BK21), KAIST, Daejeon 305-701, Korea Fax: (þ82) 42869 2810; E-mail: pkdr@kaist.ac.kr; ischoi@kaist.ac.kr 2 Department of Polymer Science and Engineering, Pusan National University, Busan 609-735, Korea Received: August 31, 2005; Revised: October 27, 2005; Accepted: October 27, 2005; DOI: 10.1002/marc.200500614 Keywords: ligand effects; metallocene catalysts; nanotubes; polyethylene (PE); polymerization Introduction Group 4-based, homogeneous single-site catalysts show highly catalytic activity for olefin polymerization. [1,2] In most cases, the catalytic precursor is a metallocene com- plex, composed of a group 4 metal (such as Ti, Zr, and Hf), two aromatic five-membered rings as an ancillary ligand and two halide groups as a leaving group. Usually the ancillary ligands at the metal center are aromatic cyclo- pentadiene-type groups (Cp). The variation of ancillary ligands, Cp rings, by introduction of proper substituents or design of a new-type ligand, changes not only steric but also electronic environments of the metal center, leading to the change in the nature of a polymerization catalyst. [1d,3] For example, isotactic [4] and syndiotactic poly(propylene)s [5] could controllably be generated by means of C 2 - and C s -symmetric ansa-metallocene complexes. A zirconocene complex derivatized with the amine group, which interacted with the Al center of co-catalyst, produced polyethylene (PE) with a bimodal distribution of molecular weights (MWs), [6] and the MW of polymers could be controlled by the variation of substituents of ancillary ligands. [7,8] The polymerization behaviors and the properties of polymeri- zation products, therefore, can be controlled primarily by the variation of the Cp rings. In this respect, the development of new metallocene-based catalysts by the modification of ancillary ligands enables us to produce custom-designed and high-valued polymers, such as copo- lymers, functionalized polymers, and high-MW polymers. However, the chemical design and modification of ligands requires very long and complicated synthetic steps, which hamper facile modifications of ligands and lowering of commercialization costs. Therefore, the development of a method for modifying catalysts through simple synthetic routes would be beneficial or desirable in the industrial sectors. Due to the unique mechanical, electrical, thermal, and optical properties, carbon nanotubes (CNTs) have been investigated for CNT/polymer composites, nanoelectronics, electron field emitters, chemical sensors, and other applica- tions. [9,10] In addition, because CNTs show a good electron Summary: We report a simple method for tuning catalytic property of a metallocene-based catalyst, Cp 2 ZrCl 2 , for ethyl- ene polymerization by the direct adsorption of Cp 2 ZrCl 2 onto multi-walled carbon nanotubes (MWCNTs). The direct interactions between MWCNTs and the Cp rings of Cp 2 ZrCl 2 controlled the polymerization behaviors, and we could generate polyethylene with an extremely high molecular weight ( M w ¼ 1 000 000) at 30 8C and under 1 atm of ethylene gas. Preparation of Cp 2 ZrCl 2 -MWCNT. Macromol. Rapid Commun. 2006, 27, 47–50 ß 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Communication DOI: 10.1002/marc.200500614 47