Lamp vs Laser: A Visible Light Photoinitiator That Promotes Radical Polymerization at Low Intensities and Cationic...

Area of Science:

• Polymer Chemistry
• Photochemistry
• Organic Synthesis

Background:

• Visible light-responsive photoinitiators are crucial for controlled polymerization.
• Anthraquinone derivatives offer tunable photochemical properties.
• Dual-mode initiation (cationic and radical) is highly desirable for advanced polymer synthesis.

Purpose of the Study:

• To investigate the dual-mode polymerization capabilities of 1-tosyloxy-2-methoxy-9,10-anthraquinone (QT) under varying visible light intensities.
• To demonstrate the controlled synthesis of polymers via cationic and radical pathways using a single photoinitiator.
• To synthesize a copolymer using a one-pot procedure by switching between polymerization mechanisms.

Main Methods:

• Utilizing 1-tosyloxy-2-methoxy-9,10-anthraquinone (QT) as a photoinitiator under different visible light irradiation intensities (high vs. low).
• Investigating the generation of para-toluenesulfonic acid (cationic initiation) under high-intensity light.
• Observing the photooxidation of DMSO to generate methyl radicals (radical initiation) under low-intensity light.
• Performing cationic ring-opening polymerization of lactones and RAFT polymerization of acrylates.
• Synthesizing a copolymer through a one-pot sequential or switchable polymerization process.

Main Results:

• QT successfully mediated cationic polymerization of lactones under high-intensity visible light via a two-photon excitation mechanism generating acid.
• QT initiated radical polymerization of acrylates under low-intensity visible light by photooxidizing DMSO and generating methyl radicals.
• The study demonstrated the ability to switch between cationic and radical polymerization mechanisms by controlling light intensity.
• A copolymer was successfully synthesized using a one-pot procedure, showcasing the practical application of QT's dual capability.

Conclusions:

• 1-tosyloxy-2-methoxy-9,10-anthraquinone (QT) acts as a versatile photoinitiator, enabling both cationic and radical polymerizations.
• Light intensity is a critical parameter for controlling the polymerization mechanism mediated by QT.
• The developed one-pot procedure offers a streamlined approach for synthesizing complex polymer architectures, including copolymers.