An orthogonal combination of cationic and radical RAFT polymerizations is used to synthesize bottlebrush polymers using two distinct RAFT agents. Selective consumption of the first RAFT agent is used to control the cationic RAFT polymerization of a vinyl ether monomer bearing a secondary dormant RAFT agent, which subsequently allows side‐chain polymers to be grafted from the pendant RAFT agent by a radical‐mediated RAFT polymerization of a different monomer, thus completing the synthesis of bottlebrush polymers. The high efficiency and selectivity of the cationic and radical RAFT polymerizations allow both polymerizations to be conducted in one‐pot tandem without intermediate purification.
Alcohol mediated degenerate chain transfer controlled cationic polymerisation of para -alkoxystyrene
In this report we demonstrate methanol as an effective degenerative chain transfer agent to control the cationic polymerisation (initiated by triflic acid) of electron rich p -alkoxy-styrenes, such as p -methoxystyrene ( p -MOS). Kinetic analysis revealed that an induction period occurs initially during which free cationic polymerisation occurs at low monomer conversion before proceeding through the pseudo first order rate, analogous to the RAFT mechanism. Ethanol and isopropanol also demonstrated excellent control ( Đ > 1.30), however, with an apparent increase in experimental molecular weight. Furthermore, methanol controlled polymers were successfully chain extended upon sequential monomer addition, demonstrating the ‘livingness’ of the alcohol mediated cationic polymerisation.
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- Award ID(s):
- 1808055
- NSF-PAR ID:
- 10107234
- Date Published:
- Journal Name:
- Polymer Chemistry
- Volume:
- 10
- Issue:
- 30
- ISSN:
- 1759-9954
- Page Range / eLocation ID:
- 4126 to 4133
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract An orthogonal combination of cationic and radical RAFT polymerizations is used to synthesize bottlebrush polymers using two distinct RAFT agents. Selective consumption of the first RAFT agent is used to control the cationic RAFT polymerization of a vinyl ether monomer bearing a secondary dormant RAFT agent, which subsequently allows side‐chain polymers to be grafted from the pendant RAFT agent by a radical‐mediated RAFT polymerization of a different monomer, thus completing the synthesis of bottlebrush polymers. The high efficiency and selectivity of the cationic and radical RAFT polymerizations allow both polymerizations to be conducted in one‐pot tandem without intermediate purification.
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Abstract Gaining temporal control over chain growth is a key challenge in the enhancement of controlled living polymerizations. Though research on photocontrolled polymerizations is still in its infancy, it has already proven useful in the development of previously inaccessible materials. Photocontrol has now been extended to cationic polymerizations using 2,4,6‐triarylpyrylium salts as photocatalysts. Despite the ability to stop polymerization for a short time, monomer conversion was observed over long dark periods. Improved catalyst systems based on Ir complexes give optimal temporal control over chain growth. The excellent stability of these complexes and the ability to tune the excited and ground state redox potentials to regulate the number of monomer additions per cation formed allows polymerization to be halted for more than 20 hours. The excellent stability of these iridium catalysts in the presence of more nucleophilic species enables chain‐end functionalization of these polymers.
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Abstract Gaining temporal control over chain growth is a key challenge in the enhancement of controlled living polymerizations. Though research on photocontrolled polymerizations is still in its infancy, it has already proven useful in the development of previously inaccessible materials. Photocontrol has now been extended to cationic polymerizations using 2,4,6‐triarylpyrylium salts as photocatalysts. Despite the ability to stop polymerization for a short time, monomer conversion was observed over long dark periods. Improved catalyst systems based on Ir complexes give optimal temporal control over chain growth. The excellent stability of these complexes and the ability to tune the excited and ground state redox potentials to regulate the number of monomer additions per cation formed allows polymerization to be halted for more than 20 hours. The excellent stability of these iridium catalysts in the presence of more nucleophilic species enables chain‐end functionalization of these polymers.
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Abstract Introduction Condensed tannins (CTs) are proanthocyanidin heteropolymers that are widely distributed among plants. Their biochemical properties are determined by molecular structure (e.g. polymer size, hydroxylation, stereochemistry). In
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P. tremuloides P. tremuloides Results Populus tremuloides Conclusion This thiolysis‐UPLC‐PDA‐(−)esiMS method was optimised for analysis of CT polymer size, hydroxylation, stereochemistry, and total concentration in
Populus foliage. It revealed significant variation in each of these properties amongP. tremuloides
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9py00480g
