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Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers
Published on: December 16, 2022
Tandem ring-opening/ring-closing metathesis polymerization: relationship between monomer structure and reactivity
Hyeon Park1, Ho-Keun Lee, Tae-Lim Choi
1Department of Chemistry, Seoul National University, Seoul 151-747, Korea.
Journal of the American Chemical Society
|July 13, 2013
Summary
Monomer design significantly impacts olefin metathesis polymerization. This study reveals how structural changes in monomers containing cycloalkene and alkyne groups influence tandem ring-opening/ring-closing metathesis polymerization rates and post-modification reactivity.
Area of Science:
- Polymer Chemistry
- Organic Synthesis
- Materials Science
Background:
- Cycloalkenes with low ring strain and 1-alkynes are typically poor monomers for olefin metathesis polymerization.
- Concerted functional groups within a single molecule can enhance metathesis polymerization efficiency.
- Previous work demonstrated rapid tandem ring-opening/ring-closing metathesis (RO/RCM) polymerization of a cyclohexene-propargyl monomer via a relay mechanism, achieving living polymerization with a third-generation Grubbs catalyst.
Purpose of the Study:
- To investigate the effect of monomer structural modifications on tandem RO/RCM polymerization.
- To elucidate the mechanism of the tandem polymerization process.
- To explore the structure-reactivity relationships governing polymerization and post-modification reactions.
Main Methods:
- Synthesis and characterization of various monomers with modified cycloalkene and alkyne moieties.
- Olefin metathesis polymerization using Grubbs catalysts.
- Kinetic studies to determine polymerization rates.
- End-group analysis via proton nuclear magnetic resonance ((1)H NMR) spectroscopy to determine polymerization mechanism.
- Diels-Alder reaction studies to assess polymer post-modification reactivity.
Main Results:
- Monomer structure, including cycloalkene ring size, alkyne length, and linker units, significantly affects polymerization rates.
- Structural modifications also influence the reactivity of post-polymerization Diels-Alder reactions.
- End-group analysis confirmed an alkyne-first pathway for the tandem RO/RCM polymerization.
- Successful polymerization of sterically hindered monomers yielded polymers with tetrasubstituted cycloalkene units.
Conclusions:
- The study establishes a dramatic structure-reactivity relationship in tandem RO/RCM polymerization.
- The alkyne-first mechanism provides a basis for understanding these structure-reactivity correlations.
- This research enables the design of novel monomers for controlled synthesis of polymers with tailored properties and functionalities.
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