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This tutorial deals initially with a comparison of the mechanistic aspects of living and immortal polymerization processes. The living polymerization pathway originated with the anionic polymerization of styrene by Szwarc, whereas immortal polymerization was first described by Inoue for the homopolymerization of epoxides using an aluminum complex. A similar behavior would be anticipated for the copolymerization of epoxides and carbon dioxide catalyzed by well-defined metal complexes. The major difference between these two pathways is rapid and reversible chain transfer reactions involving protic impurities or additives in the latter case, that is, the stoichiometry of the monomer/initiator ratio changes as a function of the nature and concentration of the chain transfer agent (CTA). For instance, in early studies of the copolymerization of epoxides and CO 2 where adventitious water was present in the copolymerization reactions, there was little control of the molecular weight of the resulting copolymer product. Presently, the presence of chain transfer with protic CTAs during the copolymerization of epoxides and CO 2 is a major positive factor in this process's commercialization. Specifically, this represents an efficient production of polyols for the synthesis of CO 2 -based polyurethanes. Studies of the use of various CTAs in the synthesis of designer polymeric materials from CO 2 and epoxides are summarized herein.
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Radical ring-opening polymerization of sustainably-derived thionoisochromanone
We present the synthesis, characterization and radical ring-opening polymerization (rROP) capabilities of thionoisochromanone (TIC), a fungi-derivable thionolactone. TIC is the first reported six-membered thionolactone to readily homopolymerize under free radical conditions without the presence of a dormant comonomer or repeated initiation. Even more, the resulting polymer is fully degradable under mild, basic conditions. Computations providing molecular-level insights into the mechanistic and energetic details of polymerization identified a unique S , S , O -orthoester intermediate that leads to a sustained chain-end. This sustained chain-end allowed for the synthesis of a block copolymer of TIC and styrene under entirely free radical conditions without explicit radical control methods such as reversible addition–fragmentation chain transfer polymerization (RAFT). We also report the statistical copolymerization of ring-retained TIC and styrene, confirmed by elemental analysis and energy-dispersive X-ray spectroscopy (EDX). Computations into the energetic details of copolymerization indicate kinetic drivers for ring-retaining behavior. This work provides the first example of a sustainable feedstock for rROP and provides the field with the first six-membered monomer susceptible to rROP, expanding the monomer scope to aid our fundamental understanding of thionolactone rROP behavior.
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- PAR ID:
- 10420365
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 14
- Issue:
- 21
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 5689 to 5698
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2SC06040J
