Synthesis of Cyclopentadienyl Capped Polyethylene and Subsequent Block Copolymer Formation Via Hetero Diels-Alder (HDA) Chemistry a Edgar Espinosa, Mathias Glassner, Christophe Boisson,* Christopher Barner-Kowollik,* Franck D’Agosto* Communication Dr. C. Boisson, Dr. F. D’Agosto, E. Espinosa Laboratoire de Chimie Catalyse Polyme `res et Proce ´de ´s (C2P2), Universite ´ de Lyon, Universite ´ Lyon 1, CPE Lyon, CNRS UMR 5265, Equipe LCPP Bat 308F, 43 Bd du 11 Novembre 1918, F-69616 Villeurbanne, France E-mail: boisson@lcpp.cpe.fr, dagosto@lcpp.cpe.fr a Supporting Information for this article is available from the Wiley Online Library or from the author. Prof. C. Barner-Kowollik, M. Glassner Preparative Macromolecular Chemistry, Institut fu ¨r Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstr. 18, 76128 Karlsruhe, Germany E-mail: christopher.barner-kowollik@kit.edu In the current contribution it is demonstrated – for the first time – that poly(ethylene) ( M n ¼ 1 400 as well as 2 800 g  mol 1 , PDI ¼ 1.2) can be readily equipped with highly reactive cyclopentadienyl (Cp) end groups. The Cp terminal poly(ethylene) can subsequently be reacted in an efficient hetero Diels- Alder (HDA) reaction with macromolecules (poly(isobornyl acrylate) ( M n ¼ 4 600 g  mol 1 , PDI ¼ 1.10) and poly(styrene) ( M n ¼ 6 300 g  mol 1 , PDI ¼ 1.13) featuring strongly electron withdrawing thiocar- bonyl thio end groups, prepared via reversible addition fragmentation chain transfer (RAFT) polymeri- zation employing benzylpyridin-2-yldithioformate (BPDF) as transfer agent. The resulting block copolymers have been analyzed via high-temperature size exclusion chromatography (SEC) as well as nuclear magnetic resonance (NMR) spectroscopy. The current system allows for the removal of the excess of the non- poly(ethylene) containing segment via filtration of the poly(ethylene)-containing block copolymer. However, the reaction temperatures need to be judiciously selected. Characterization of the generated block copo- lymers at elevated temperatures can lead – depending on the block copolymer type – to the occurrence of retro Diels-Alder processes. The present study thus demon- strates that RAFT-HDA ligation can be effectively employed for the generation of block copolymers con- taining poly(ethylene) segments. Macromol. Rapid Commun. 2011, 32, 1447–1453 ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com DOI: 10.1002/marc.201100310 1447