Thiol-ene photofunctionalization of 1,4-polymyrcene
- 1,4-Polymyrcene was synthesized by anionic polymerization of -myrcene and was subjected to photochemical functionalization with various thiols (i.e. methyl thioglycolate, methyl 3-mercaptopropionate, butyl 3-mercaptopropionate, ethyl 2-mercaptopropionate and 2-methyl-2-propanethiol) using benzophenone/UV light as the radical source. The yield of thiol addition to the trisubstituted double bonds of 1,4-polymyrcene decreased in the order 1 degrees thiol (ca 95%) > 2 degrees thiol (ca 80%) > 3 degrees thiol (<5%), due to the reversibility of the thiol-ene reaction. Remarkably, thiol addition to the side-chain double bonds was 8 - 10 times (1 degrees thiol) or 24 times (2 degrees thiol) faster than to the main-chain double bonds, which can be explained by the different accessibility of the double bonds and steric hindrance. Despite the use of a 10-fold excess of thiol with respect to myrcene units, the thiol-ene addition was accompanied by chain coupling reactions, which in the extreme case of 3 degrees thiol (or in the absence of thiol)1,4-Polymyrcene was synthesized by anionic polymerization of -myrcene and was subjected to photochemical functionalization with various thiols (i.e. methyl thioglycolate, methyl 3-mercaptopropionate, butyl 3-mercaptopropionate, ethyl 2-mercaptopropionate and 2-methyl-2-propanethiol) using benzophenone/UV light as the radical source. The yield of thiol addition to the trisubstituted double bonds of 1,4-polymyrcene decreased in the order 1 degrees thiol (ca 95%) > 2 degrees thiol (ca 80%) > 3 degrees thiol (<5%), due to the reversibility of the thiol-ene reaction. Remarkably, thiol addition to the side-chain double bonds was 8 - 10 times (1 degrees thiol) or 24 times (2 degrees thiol) faster than to the main-chain double bonds, which can be explained by the different accessibility of the double bonds and steric hindrance. Despite the use of a 10-fold excess of thiol with respect to myrcene units, the thiol-ene addition was accompanied by chain coupling reactions, which in the extreme case of 3 degrees thiol (or in the absence of thiol) resulted in the formation of insoluble crosslinked material. As an example, a methyl-thioglycolate-functionalized 1,4-polymyrcene was saponified/crosslinked to give submicron polyelectrolyte particles in dilute alkaline solution. (c) 2018 Society of Chemical Industry…
Author details: | Aleksandar MaticGND, Helmut SchlaadORCiDGND |
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DOI: | https://doi.org/10.1002/pi.5534 |
ISSN: | 0959-8103 |
ISSN: | 1097-0126 |
Title of parent work (English): | Polymer international |
Publisher: | Wiley |
Place of publishing: | Hoboken |
Publication type: | Article |
Language: | English |
Date of first publication: | 2018/01/12 |
Publication year: | 2018 |
Release date: | 2021/12/08 |
Tag: | photochemistry; polymyrcene; regioselectivity; thiol-ene |
Volume: | 67 |
Issue: | 5 |
Number of pages: | 6 |
First page: | 500 |
Last Page: | 505 |
Funding institution: | Zentrales Innovationsprogramm Mittelstand (ZIM) of the German Federal Ministry for Economic Affairs and Energy (BMWi) [ZF4189301SL5] |
Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie |
DDC classification: | 5 Naturwissenschaften und Mathematik / 54 Chemie / 540 Chemie und zugeordnete Wissenschaften |
Peer review: | Referiert |