Switchable RAFT Polymerization Employing Photoresponsive HABI as a Mediator.

Area of Science:

• Polymer Chemistry
• Photochemistry
• Radical Polymerization

Background:

• Developing switchable polymerization methods is crucial for advanced material synthesis.
• Photoactivation strategies for reversible addition-fragmentation chain transfer (RAFT) polymerization are of significant interest.
• Existing methods like PET-RAFT polymerization offer light-controlled polymerization but can be improved for temporal control.

Purpose of the Study:

• To introduce a novel photo-deactivation strategy for reversible addition-fragmentation chain transfer (RAFT) polymerization.
• To demonstrate switchable RAFT polymerization using a photoresponsive hexaarylbiimidozole (HABI) mediator.
• To investigate the mechanism of photo-deactivation RAFT (PD-RAFT) polymerization for precise temporal control.

Main Methods:

• Utilized photoresponsive hexaarylbiimidozole (HABI) as a mediator for RAFT polymerization.
• Employed UV light to reversibly quench propagating radicals, enabling photo-deactivation.
• Conducted repeated ON/OFF experiments to demonstrate switchable polymerization control.
• Applied Electron Spin Resonance (ESR), Nuclear Magnetic Resonance (NMR), Gel Permeation Chromatography (GPC), and MALDI-TOF-MS for mechanistic studies.

Main Results:

• Successfully demonstrated switchable RAFT polymerization using the PD-RAFT method.
• Showcased temporal stopping of polymerization upon UV light activation (ON state).
• Confirmed reversible radical quenching by HABI, leading to controlled polymerization.
• Provided mechanistic insights into PD-RAFT polymerization through comprehensive analytical studies.

Conclusions:

• The developed photo-deactivation RAFT (PD-RAFT) polymerization offers a new route for switchable polymer synthesis.
• HABI acts as an effective photoresponsive mediator for reversible control of radical polymerization.
• PD-RAFT polymerization provides precise temporal control, enabling repeated ON/OFF cycles for polymerization regulation.