Insertion of degradable thioester linkages into styrene and methacrylate polymers: insights into the reactivity of thionolactones
Insertion of degradable thioester linkages into styrene and methacrylate polymers: insights into the reactivity of thionolactones
The thionolactone 3,3-dimethyl-2,3-dihydro-5H-benzo[e][1,4]dioxepine-5-thione (DBT) is shown to radically homopolymerize, copolymerize rapidly with acrylates and styrene, and, for the first time, copolymerize with methacrylates, introducing a degradable thioester backbone functionality. Surprisingly, the aminolysis of DBT homopolymers was accompanied by the intramolecular ether cleavage, leading to the formation of 2,2-dimethylthiirane and salicylamides. The rapid copolymerization with styrene was exploited to produce degradable copolymers through free-radical polymerization in a starve-fed semibatch setup. The higher reactivity of DBT compared to the current benchmark thionolactone dibenzo[c,e]oxepine-5(7H)-thione (DOT) was inconsistent with the expected electron-donating effect of the alkoxy substituent in DBT. Using single-crystal XRD structure analysis and DFT modeling, this study rationalized the higher reactivity of DBT by (i) better stabilization of the intermediate radical in DBT by means of a better overlap with the adjacent aromatic, which shifts the addition equilibrium to the right; (ii) an increased ring strain in DBT compared to DOT, which drives the ring-opening; and (iii) better reinitiating efficiency of the tertiary alkyl open-ring radical of DBT compared to the benzylic radical of DOT. These insights are expected to facilitate the development of further thionolactone monomers with tailored copolymerization behavior.
9787-9795
Rix, Matthew F.I.
95eb38a1-7601-4f3c-989f-b611a3b7ba1f
Collins, Kyle
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Higgs, Samuel J.
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Dodd, Eleanor M.
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Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Bingham, Nathaniel M.
450862ab-a95e-4ba7-a441-b7740a4631f1
Roth, Peter J.
90e18c6c-d96a-4b03-bdee-5b5e8ba8374b
12 December 2023
Rix, Matthew F.I.
95eb38a1-7601-4f3c-989f-b611a3b7ba1f
Collins, Kyle
24b277c1-d77a-4a23-880a-6028422468dd
Higgs, Samuel J.
de3042ae-90d6-4789-8382-01d038927eee
Dodd, Eleanor M.
a0ad89d4-bdb7-4969-9c69-a03051df7b86
Coles, Simon J.
3116f58b-c30c-48cf-bdd5-397d1c1fecf8
Bingham, Nathaniel M.
450862ab-a95e-4ba7-a441-b7740a4631f1
Roth, Peter J.
90e18c6c-d96a-4b03-bdee-5b5e8ba8374b
Rix, Matthew F.I., Collins, Kyle, Higgs, Samuel J., Dodd, Eleanor M., Coles, Simon J., Bingham, Nathaniel M. and Roth, Peter J.
(2023)
Insertion of degradable thioester linkages into styrene and methacrylate polymers: insights into the reactivity of thionolactones.
Macromolecules, 56 (23), .
(doi:10.1021/acs.macromol.3c01811).
Abstract
The thionolactone 3,3-dimethyl-2,3-dihydro-5H-benzo[e][1,4]dioxepine-5-thione (DBT) is shown to radically homopolymerize, copolymerize rapidly with acrylates and styrene, and, for the first time, copolymerize with methacrylates, introducing a degradable thioester backbone functionality. Surprisingly, the aminolysis of DBT homopolymers was accompanied by the intramolecular ether cleavage, leading to the formation of 2,2-dimethylthiirane and salicylamides. The rapid copolymerization with styrene was exploited to produce degradable copolymers through free-radical polymerization in a starve-fed semibatch setup. The higher reactivity of DBT compared to the current benchmark thionolactone dibenzo[c,e]oxepine-5(7H)-thione (DOT) was inconsistent with the expected electron-donating effect of the alkoxy substituent in DBT. Using single-crystal XRD structure analysis and DFT modeling, this study rationalized the higher reactivity of DBT by (i) better stabilization of the intermediate radical in DBT by means of a better overlap with the adjacent aromatic, which shifts the addition equilibrium to the right; (ii) an increased ring strain in DBT compared to DOT, which drives the ring-opening; and (iii) better reinitiating efficiency of the tertiary alkyl open-ring radical of DBT compared to the benzylic radical of DOT. These insights are expected to facilitate the development of further thionolactone monomers with tailored copolymerization behavior.
Text
rix-et-al-2023-insertion-of-degradable-thioester-linkages-into-styrene-and-methacrylate-polymers-insights-into-the
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Accepted/In Press date: 15 November 2023
e-pub ahead of print date: 30 November 2023
Published date: 12 December 2023
Additional Information:
Funding Information:
The authors gratefully acknowledge studentship funding for M.F.I.R. from the University of Surrey and from Syngenta, and Dr Annette Christie, Dr Nick Mulholland, and Dr Chris Lindsay (Syngenta) for continued support.
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Local EPrints ID: 486055
URI: http://eprints.soton.ac.uk/id/eprint/486055
ISSN: 0024-9297
PURE UUID: 077bc841-3f9a-4d27-ad20-a95c2b2eb465
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Date deposited: 08 Jan 2024 17:34
Last modified: 18 Mar 2024 02:50
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Contributors
Author:
Matthew F.I. Rix
Author:
Kyle Collins
Author:
Samuel J. Higgs
Author:
Eleanor M. Dodd
Author:
Nathaniel M. Bingham
Author:
Peter J. Roth
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