Chan, D.H.H., Cockram, A.A., Gibson, R.R. et al. (4 more authors) (2021) RAFT aqueous emulsion polymerization of methyl methacrylate : observation of unexpected constraints when employing a non-ionic steric stabilizer block. Polymer Chemistry, 12 (40). pp. 5760-5769. ISSN 1759-9954
Abstract
The RAFT aqueous emulsion polymerization of methyl methacrylate (MMA) is conducted at 70 °C using poly(glycerol monomethacrylate) (PGMA) as a steric stabilizer block. This non-ionic precursor has previously proved to be highly effective for the RAFT aqueous emulsion polymerization of various vinyl monomers such as benzyl methacrylate (BzMA), 2,2,2-trifluoroethyl methacrylate (TFEMA), isopropylideneglycerol monomethacrylate (IPGMA) or glycidyl methacrylate. However, an unexpected constraint was encountered in the case of MMA. Targeting a degree of polymerization (DP) of 20 to 100 for the PMMA block led to colloidal dispersions of kinetically-trapped spherical nanoparticles ranging in size from 17 nm to 31 nm. On the other hand, targeting DPs above 100 invariably led to the formation of highly flocculated spherical nanoparticles. This rather limited DP range is in striking contrast to the much higher DPs that can be targeted without loss of colloidal stability when using more hydrophobic monomers such as BzMA, TFEMA or IPGMA. The same flocculation problem was also evident when employing a PGMA precursor containing an anionic carboxylate end-group, but a series of colloidally stable dispersions could be obtained when using an anionic poly(methacrylic acid) stabilizer. Finally, the efficient removal of RAFT end-groups from PGMA50-PMMA80 nanoparticles was achieved by visible light irradiation using a blue LED source (λ = 405 nm). UV GPC studies confirmed that up to 87% dithiobenzoate end-groups can be removed from such nanoparticles within 12 h at 80 °C. On the other hand, using excess H2O2 under the same conditions only led to 24% end-group removal. This is because this water-soluble reagent has restricted access to the hydrophobic PMMA cores.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2021 The Royal Society of Chemistry. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/). |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Chemistry (Sheffield) |
Funding Information: | Funder Grant number Engineering and Physical Sciences Research Council EP/R003009/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 11 Oct 2021 13:51 |
Last Modified: | 10 Mar 2022 16:58 |
Status: | Published |
Publisher: | Royal Society of Chemistry |
Refereed: | Yes |
Identification Number: | 10.1039/d1py01008e |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:178972 |