Cyano-functionalized polyethylenes from ethylene/acrylamide copolymerization.

Area of Science:

• Polymer Chemistry
• Organometallic Catalysis
• Materials Science

Background:

• Synthesizing functionalized polyethylenes via coordination copolymerization is attractive but challenging due to catalyst poisoning by functional groups.
• Existing methods for cyano-functionalized polyethylene synthesis, like ethylene/acrylonitrile copolymerization, suffer from low activity, often relying on palladium catalysis.
• Functional group compatibility with catalysts remains a significant hurdle in polyolefin synthesis.

Purpose of the Study:

• To develop a highly active and robust catalytic system for synthesizing cyano-functionalized polyethylenes.
• To overcome catalyst poisoning issues associated with traditional methods.
• To elucidate the polymerization mechanism for improved catalyst design.

Main Methods:

• Utilized a binuclear nickel catalyst for ethylene/acrylamide copolymerization.
• Conducted extensive polymer characterizations including NMR and GPC.
• Performed mechanistic investigations involving control experiments, deuterium labeling, and computational studies.

Main Results:

• Achieved high activity (4.1 × 10^6 g/(mol cat·h)) in ethylene/acrylamide copolymerization, yielding >99% cyano-functionalized polyethylenes.
• Confirmed significant chain transfer and in-situ conversion of amide to nitrile groups during catalysis.
• Demonstrated that the binuclear Ni catalyst system circumvents catalyst poisoning.

Conclusions:

• The developed binuclear Ni catalysis enables efficient synthesis of cyano-functionalized polyethylenes.
• An isomerization-mediated chain transfer polymerization (ICTP) pathway involving amide-to-nitrile conversion and catalyst regeneration was proposed and supported.
• This approach offers a promising alternative for producing functional polyolefins with enhanced properties.