Reversible Deactivation Radical Polymerization of Monomers Containing Activated Aziridine Groups.

Area of Science:

• Polymer Chemistry
• Organic Synthesis
• Materials Science

Background:

• Polymers with activated aziridine groups are valuable for creating α-substituted-β-amino-functionalized materials.
• The aziridine ring's reactivity towards nucleophiles makes it a key functional group for further chemical modification.

Purpose of the Study:

• To investigate the controlled polymerization of aziridine-containing styrenic monomers using various reversible deactivation radical polymerization (RDRP) techniques.
• To evaluate the impact of protecting the aziridine nitrogen atom on polymerization control and polymer characteristics.

Main Methods:

• Polymerization of 2-(4-vinylphenyl)aziridine (VPA) and N-mesyl-2-(4-vinylphenyl)aziridine (NMVPA) using low-catalyst-concentration atom transfer radical polymerization (LCC-ATRP), reversible addition-fragmentation chain-transfer (RAFT), and nitroxide-mediated polymerization (NMP).
• Analysis of polymer molecular weight distribution, polydispersity, and structural integrity.

Main Results:

• VPA polymerization using LCC-ATRP and RAFT resulted in ill-defined polymers due to aziridine side reactions.
• NMP of VPA yielded polymers with narrow molecular weight distribution at low conversions, but branching and cross-linking occurred at higher conversions.
• Protecting the aziridine nitrogen with a methanesulfonyl (mesyl) group (NMVPA) enabled the synthesis of well-defined linear homopolymers via RAFT and NMP.
• LCC-ATRP of NMVPA remained uncontrolled due to persistent side reactions.

Conclusions:

• The methanesulfonyl group effectively suppresses undesirable side reactions of the aziridine ring during controlled radical polymerization.
• RAFT and NMP are suitable methods for synthesizing well-defined polymers from N-mesyl-2-(4-vinylphenyl)aziridine.
• Further optimization is needed for LCC-ATRP of aziridine-containing monomers.