Desulfurization-bromination: direct chain-end modification of RAFT polymers

Area of Science:

• Polymer Chemistry
• Organic Synthesis

Background:

• Controlled radical polymerization (CRP) techniques like reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP) are crucial for synthesizing polymers with defined architectures.
• Chain-end functionalization is essential for creating advanced polymer materials, including block copolymers.
• Bridging different CRP techniques can expand the scope of accessible polymer structures.

Purpose of the Study:

• To develop a simple and efficient method for converting thiol and thiocarbonylthio functional groups to bromides.
• To demonstrate the utility of this transformation for modifying polymer chain ends prepared by RAFT polymerization.
• To enable the synthesis of chain-end functionalized block copolymers by combining RAFT and ATRP.

Main Methods:

• Utilized stable and commercially available brominating reagents for the transformation.
• Applied the procedure to small molecule thiols (primary, secondary, tertiary) and polystyrene (PS) homopolymers and block copolymers.
• Investigated the activity of the introduced terminal bromide for subsequent chain extension via ATRP.

Main Results:

• Achieved quantitative conversion of thiols and thiocarbonylthio groups to bromides under mild conditions.
• Successfully performed direct chain-end bromination of PS synthesized by RAFT polymerization.
• Demonstrated that the terminal bromide remained active for subsequent ATRP, allowing for chain extension.

Conclusions:

• The developed method provides a facile route to introduce terminal bromides onto polymers synthesized by RAFT.
• This transformation effectively bridges RAFT and ATRP, enabling the synthesis of complex polymer architectures.
• Facilitates the preparation of chain-end functionalized block copolymers not easily accessible through single CRP methods.