Vitamin B₁₂ Derivative Enables Cobalt-Catalyzed Atom Transfer Radical Polymerization

Area of Science:

• Polymer Chemistry
• Organometallic Chemistry

Background:

• Cobalt complexes control radical polymerization by reversibly deactivating chains, but require stoichiometric amounts.
• Stoichiometric cobalt use limits the synthesis of well-defined polymers.

Purpose of the Study:

• To develop a catalytic strategy for controlled radical polymerization using cobalt.
• To utilize cobalt as a catalyst in halogen atom transfer radical polymerization (ATRP).

Main Methods:

• Employed a hydrophobic vitamin B12 analogue (heptamethyl ester cobyrinate) as a cobalt precatalyst.
• Investigated the polymerization of acrylate monomers using alkyl halide initiators.
• Optimized catalyst efficiency with bromide anions.

Main Results:

• Achieved controlled polymerization of acrylates using low catalyst concentrations (5 mol %).
• Demonstrated significantly improved polymerization efficiency with bromide anion addition.
• Synthesized polymers with low dispersity values (<1.2).

Conclusions:

• Cobalt can effectively catalyze halogen atom transfer radical polymerization.
• This catalytic system offers a more efficient route to well-defined polymers.
• The findings open new avenues for catalytic polymer synthesis.