Concentration-Driven Ring Expansion Metathesis Polymerization via Tunable Ring Transfer Processes.

Area of Science:

• Polymer Chemistry
• Catalysis
• Materials Science

Background:

• Ring expansion metathesis polymerization (REMP) is vital for creating cyclic polymer architectures.
• Cyclic Ru-benzylidene catalyst CB6 offers enhanced stability and polymerization rates.
• CB6 exhibits an unusual molar mass evolution, decreasing over time.

Purpose of the Study:

• To mechanistically understand the polymerization profiles of CB6 in REMP.
• To investigate the ring transfer steps responsible for CB6's unique molar mass behavior.
• To establish control over REMP for novel cyclic material development.

Main Methods:

• Mechanistic studies of CB6 polymerization.
• Analysis of molar mass evolution profiles.
• Investigation of reaction concentration effects.

Main Results:

• CB6 acts as both an initiator and a catalytic ring transfer agent.
• An intricate relationship between reaction concentration and molar mass was identified.
• High molar mass cyclic polymers are formed early, followed by a decrease.

Conclusions:

• A deeper mechanistic understanding of REMP with CB6 was achieved.
• Control over REMP is enhanced through understanding catalyst behavior.
• This work provides a toolkit for optimizing catalyst design and creating new cyclic materials.