skip to main content


This content will become publicly available on May 31, 2024

Title: 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.  more » « less
Award ID(s):
1901635 2011401
NSF-PAR ID:
10420365
Author(s) / Creator(s):
; ; ; ; ; ;
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
More Like this
  1. Abstract

    Heterocyclic hypervalent (HV) iodine(III) compounds with ICl bonds and various substituents at the N atom are synthesized and found to be very efficient chain transfer agents in the polymerization of styrene with transfer coefficients exceeding that of CCl4by 2–3 orders of magnitude, depending on the structure. The chain transfer rate coefficients are also determined. Due to the presence of thermally labile HV bonds, the compounds degrade homolytically upon heating and can initiate radical polymerization. For instance, 1‐chloro‐2‐hexyl‐1,2‐benziodazol‐3(2H)‐one, is used in the polymerization of styrene, which yields low molecular weight polymers with alkyl chloride groups at the α‐ (initiation) and the ω‐chain ends (transfer). Chain‐end functionalization reactions with azide and chain extension under low‐catalyst‐concentration atom transfer radical polymerization (ATRP) conditions of the prepared telechelic polymers are carried out. The same initiator/chain transfer agent is successfully employed in the synthesis of highly branched polymers with multiple alkyl chloride‐type chain ends when added to mixtures of styrene and 1,4‐divinylbenzene containing 10–80 mol% of the divinyl crosslinker, or even pure crosslinker. In all cases, soluble hyperbranched polymers are obtained up to moderate monomer conversions. The effects of crosslinker and HV iodine(III) compound concentrations on the polymerization outcome are studied systematically.

     
    more » « less
  2. 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. 
    more » « less
  3. Abstract

    Low‐strain cyclic olefin monomers, including five‐membered, six‐membered, eight‐membered, and macrocyclic rings, have been recently exploited for the synthesis of depolymerizable polyolefins via ring‐opening metathesis polymerization (ROMP). Such polyolefins can undergo ring‐closing metathesis depolymerization (RCMD) to regenerate their original monomers. Nevertheless, the depolymerization behavior of polyolefins prepared by ROMP of seven‐membered cyclic olefins, an important class of low‐strain rings, still remains unexplored. In this study, we demonstrate the chemical recycling of polyheptenamers to cycloheptene under standard RCMD conditions. Highly efficient depolymerization of polyheptenamer was enabled by Grubbs' second‐generation catalyst in toluene. It was observed that the monomer yields increased when the depolymerization temperature increased and the starting polymer concentration was reduced. A near‐quantitative monomer regeneration (>96%) was achieved within 1 h under dilute conditions (20 mM of olefins) at 60°C. Moreover, polyheptenamer exhibited a decomposition temperature above 430°C, highlighting its potential as a new class of thermally stable and chemically recyclable polymer materials.

     
    more » « less
  4. The development of robust methods for the synthesis of chemically recyclable polymers with tunable properties is necessary for the design of next-generation materials. Polyoxazolidinones (POxa), polymers with five-membered urethanes in their backbones, are an attractive target because they are strongly polar and have high thermal stability, but existing step-growth syntheses limit molar masses and methods to chemically recycle POxa to monomer are rare. Herein, we report the synthesis of high molar mass POxa via ring-opening metathesis polymerization of oxazolidinone-fused cyclooctenes. These novel polymers show <5% mass loss up to 382–411 °C and have tunable glass transition temperatures (14–48 °C) controlled by the side chain structure. We demonstrate facile chemical recycling to monomer and repolymerization despite moderately high monomer ring-strain energies, which we hypothesize are facilitated by the conformational restriction introduced by the fused oxazolidinone ring. This method represents the first chain growth synthesis of POxa and provides a versatile platform for the study and application of this emerging subclass of polyurethanes. 
    more » « less
  5. The direct-growth technique was used to synthesize several macromonomers (MMs) employing reversible addition–fragmentation chain transfer (RAFT) polymerization by growing directly from a norbornene-functionalized chain transfer agent (CTA). We aimed to investigate the formation of bisnorbornenyl species resulting from radical termination by combination ( i.e. , coupling) during RAFT polymerization at different monomer conversion values in four types of monomers: styrene, tert -butyl acrylate, methyl methacrylate and N -acryloyl morpholine. Ring-opening metathesis polymerization (ROMP) of these MMs using Grubbs' 3rd generation catalyst (G3) at an MM : G3 ratio of 100 : 1 resulted in the formation of bottlebrush polymers. Analysis by size-exclusion chromatography (SEC) revealed high molar mass shoulders of varying intensities attributed to the incorporation of these bisnorbornenyl species to generate dimeric or higher-order bottlebrush polymer oligomers. The monomer type in the RAFT step heavily influenced the amount of these bottlebrush polymer dimers and oligomers, as did the monomer conversion value in the RAFT step: We found that the ROMP of polystyrene MMs with a target backbone degree of polymerization of 100 produced detectable coupling at ≥20% monomer conversion in the RAFT step, while it took ≥80% monomer conversion to observe coupling in the poly( tert -butyl acrylate) MMs. We did not detect coupling in the poly(methyl methacrylate) MMs, but broadening of the SEC peaks and an increase in dispersity occurred, suggesting the presence of metathesis-active alkene-containing chain ends created by disproportionation. Finally, poly( N -acryloyl morpholine) MMs, even when reaching 90% monomer conversion in the RAFT step, showed no detectable coupling in the bottlebrush polymers. These results highlight the importance of monomer choice and RAFT polymerization conditions in making MMs for ROMP grafting-through to make well-defined bottlebrush polymers. 
    more » « less