Selective Photoactivation: From a Single Unit Monomer Insertion Reaction to Controlled Polymer Architectures

Area of Science:

• Polymer Chemistry
• Organic Synthesis
• Photochemistry

Background:

• Thiocarbonylthio compounds offer unique photoactivation properties.
• Controlled radical polymerization techniques are crucial for advanced polymer design.
• Developing selective methods for complex macromolecular architectures is challenging.

Purpose of the Study:

• To implement two distinct light-mediated polymerization methodologies.
• To utilize the selective photoactivation of thiocarbonylthio compounds.
• To synthesize well-defined polymers and complex macromolecular architectures.

Main Methods:

• Single Unit Monomer Insertion (SUMI) using pheophorbide a (PheoA) photoredox catalyst under red light.
• Visible-light-mediated photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization.
• Sequential polymerization using two different catalysts (PheoA and zinc tetraphenylporphine, ZnTPP) under distinct light wavelengths.

Main Results:

• Achieved precise single unit monomer insertion into dithiobenzoate with >97% yield.
• Demonstrated selective polymerization of methacrylate backbone using PheoA.
• Successfully synthesized well-defined graft co-polymers by polymerizing pendant trithiocarbonate moieties with ZnTPP under green light.

Conclusions:

• The selectivity of photoactivation of thiocarbonylthio compounds can be effectively exploited for controlled polymerization.
• The developed SUMI and PET-RAFT methods offer precise control over polymer synthesis.
• This approach enables the creation of complex macromolecular architectures, such as graft co-polymers, with high precision.