Nickel-Catalyzed Propylene/Polar Monomer Copolymerization

Area of Science:

• Organometallic Chemistry
• Polymer Science
• Catalysis

Background:

• Nickel complexes with specific ligands are key catalysts in olefin polymerization.
• Controlling regiochemistry and incorporating polar monomers remain challenges in propylene polymerization.

Purpose of the Study:

• To synthesize and investigate nickel complexes with bidentate alkylphosphine-phenolate ligands for propylene polymerization.
• To explore the regiocontrolled copolymerization of propylene with various polar monomers using these nickel catalysts.

Main Methods:

• Synthesis of novel nickel complexes featuring bulky alkylphosphine-phenolate ligands.
• Propylene polymerization and copolymerization studies under varying conditions.
• Theoretical calculations to elucidate reaction mechanisms and stereochemical control.

Main Results:

• Bulky alkyl substituents on phosphorus atoms are essential for high regioregularity in polypropylene.
• Theoretical calculations indicate a preference for 1,2-insertion over 2,1-insertion of propylene.
• Substituent effects at the ortho position influence catalyst activity, molecular weight, and stereoregularity.
• Moderately isotactic crystalline polypropylenes ([mm] ≤ 68%) were produced.
• The system is the first to achieve nickel-catalyzed regiocontrolled copolymerization of propylene with polar monomers (e.g., but-3-en-1-ol, but-3-en-1-yl acetate, tert-butyl allylcarbamate).

Conclusions:

• Nickel complexes with bulky alkylphosphine-phenolate ligands offer precise control over propylene polymerization regiochemistry.
• This catalytic system opens new avenues for synthesizing functionalized polypropylenes through copolymerization with polar monomers.