Mechanochemical ring-opening metathesis polymerization: development, scope, and mechano-exclusive polymer synthesis

Area of Science:

• Polymer Chemistry
• Green Chemistry
• Materials Science

Background:

• Ring-opening metathesis polymerization (ROMP) is typically performed in solution.
• Solvent use in polymerization can pose environmental and economic challenges.
• Limitations in monomer solubility and miscibility can restrict polymer synthesis.

Purpose of the Study:

• To develop a solvent-free method for ROMP using mechanochemistry.
• To explore the use of ruthenium-alkylidene catalysts under solid-state conditions.
• To synthesize novel polymers, including mechano-exclusive copolymers, not accessible via traditional methods.

Main Methods:

• Mechanochemical ball milling of ruthenium-alkylidene initiators and monomers under solid-state conditions.
• Utilizing a third-generation Grubbs catalyst for efficient polymerization.
• Employing liquid-assisted grinding with minimal liquid additives to control molecular weight.

Main Results:

• Successful polymerization of various solid monomers, including ionomers, fluorous monomers, and macromonomers.
• Demonstration of direct copolymerization of immiscible ionic and hydrophobic monomers.
• Achieved high-molecular-weight polymer synthesis with minimized chain degradation using liquid-assisted grinding.

Conclusions:

• Solid-state ROMP via ball milling is a viable and green alternative to solution-phase polymerization.
• This mechanochemical approach overcomes monomer solubility limitations and enables the synthesis of unique polymer architectures.
• The method offers broad applicability for diverse monomers and facilitates the creation of mechano-exclusive polymers.