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Leveraging Electron Push-Pull Effect for Catalytic Polymerization and Degradation of a Cyclobutane Monomer System
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DOI：10.1002/anie.202405408.png)
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Abstract
En 中文
Ring-opening polymerization (ROP) offers a striking solution to solve problems encountered in step-growth condensation polymerization, including precise control over molecular weight, molecular weight distribution, and topology. This has inspired our interest in ROP of cycloalkanes with an ultimate goal to rethink polyolefins, which clearly poses a number of challenges. Practicality of ROP of cycloalkanes is actually limited by their low polymerizability and elusive mechanisms which arise from significantly varied ring size and non-polar C-C bonds in monomers. In this work, by using Lewis acid/Br & oslash;nsted base/C(sp3)-H initiator system previously developed in our laboratory, we focus on cyclobutanes and explore the positional and electronic effects of substituents on the ring, namely electron push-pull effect, in promoting controlled polymerization to afford densely functionalized poly(cyclobutanes), as well as catalytic degradation of obtained polymers for upcycling. More importantly, experiments and DFT calculations unveil considerable population of Lewis-acid-induced thermostabilized 1,4-zwitterions, which distinguish cyclobutanes from cyclopropanes and others. All these findings would shed light on catalytic synthesis and degradation of saturated all-carbon main-chain polymers, as well as small molecule transformations of cyclobutanes. DFT calculations guide to unveil the electron push-pull effect in reshaping the polymerizability of non-polymerizable cyclobutane to afford densely functionalized all-carbon main-chain polymers, as well as their degradation to afford alkene derivatives. Successful polymerization conditions consist of Lewis acid, Br & oslash;nsted base, and a C(sp3)-H initiator, while degradation proceeds with catalytic amount of an acid. image
Keywords:
ring-opening polymerization
electron push-pull effect
cyclobutane
cooperative catalysis
degradation
Journal
IF:
16.9
Papers:
5.6W
Citations:
53.0W