Leveraging Earth-Abundant Nickel for Orthogonal Polymerizations: Synthesizing Polar Polyolefin Block Copolymers

Area of Science:

• Polymer Chemistry
• Organometallic Chemistry
• Materials Science

Background:

• Palladium(II) diimine complexes enable one-pot synthesis of polar polyolefin block copolymers via distinct radical and coordination-insertion polymerization pathways.
• Replacing palladium with earth-abundant nickel for similar catalytic activity has been a significant challenge in polymer synthesis.

Purpose of the Study:

• To demonstrate the feasibility of using carbyl iminopyridyl Ni(II) complexes for synthesizing polar polyolefin block copolymers.
• To achieve selective radical and coordination-insertion polymerization pathways using nickel catalysts for a one-pot synthesis.

Main Methods:

• Synthesis and investigation of carbyl iminopyridyl Ni(II) complexes.
• Utilizing metal-organic insertion light-initiated radical polymerization (MILRad) for block copolymer synthesis.
• Characterization of polymers using techniques such as TEMPO trapping and DFT calculations for mechanistic insights.

Main Results:

• Carbyl iminopyridyl Ni(II) complexes exhibit unique selectivity for both radical and coordination-insertion polymerization pathways.
• Successful synthesis of polar polyolefin block copolymers with controlled molecular weights (49-244 kg/mol) and segment lengths.
• Demonstrated high tolerance towards acrylic monomers, forming reactive Ni(II) acryl chelates that initiate radical polymerization upon blue light irradiation.

Conclusions:

• Carbyl iminopyridyl Ni(II) complexes offer a viable and unprecedented catalytic system for the one-pot synthesis of polar polyolefin block copolymers.
• This work overcomes the previous limitations associated with using earth-abundant nickel catalysts in such polymerization processes.
• The developed MILRad approach provides a new avenue for creating advanced polymer architectures with tunable properties.