Synthesis of Cyclopentadienyl Capped Polyethylene and Subsequent Block Copolymer Formation Via Hetero Diels-Alder (HDA) Chemistry

✍ Scribed by Edgar Espinosa; Mathias Glassner; Christophe Boisson; Christopher Barner-Kowollik; Franck D'Agosto

• Book ID: 102497666
• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 273 KB
• Volume: 32
• Category: Article
• ISSN: 1022-1336
• DOI: 10.1002/marc.201100310

✦ Synopsis

Abstract

In the current contribution it is demonstrated – for the first time – that poly(ethylene) ($\overline {M} _{{\rm n}} $ = 1 400 as well as 2 800 g  ·  mol^−1^, PDI = 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) ($\overline {M} _{{\rm n}} $ = 4 600 g  ·  mol^−1^, PDI = 1.10) and poly(styrene) ($\overline {M} _{{\rm n}} $ = 6 300 g  ·  mol^−1^, PDI = 1.13) featuring strongly electron withdrawing thiocarbonyl thio end groups, prepared via reversible addition fragmentation chain transfer (RAFT) polymerization 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 copolymers at elevated temperatures can lead – depending on the block copolymer type – to the occurrence of retro Diels‐Alder processes. The present study thus demonstrates that RAFT‐HDA ligation can be effectively employed for the generation of block copolymers containing poly(ethylene) segments.

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