A Novel Branched–Hyperbranched Block Polyolefin Produced via Chain Shuttling Polymerization from Ethylene Alone

Abstract

A novel branched-hyperbranched polyethylene was synthesized via chain walking and chain shuttling polymerization by one step. In polymerization, {2,6- ⁱ Pr₂-C₆H₃N˭C(CH₃)-(CH₃)C˭N- ⁱ Pr₂-C₆H₂}NiBr₂(CatA) and {2,6-Me₂-C₆H₃N˭C(CH₃)-(CH₃)C˭N-Me₂-C₆H₂}NiBr₂(CatB) was adopted to yield branched and hyperbranched segments via chain walking polymerization at one ethylene atm and 20°C, respectively. Then the chain transfer agent(ZnEt₂) facilitated chain transfer between two active metal centers to accomplish chain shuttling polymerization of ethylene. This strategy stands out from “living”/controlled polymerization and coupling block polymers techniques for just using ethylene as monomer, carrying out under moderate polymerization and obtaining the resultant polymer with novel microstructure.

Keywords:

• Branched-hyperbranched polyethylene
• Chain shuttling
• Chain transfer
• Chain walking

Notes

^a Polymerization conditions: t _p = 30 min, 30 mL of toluene solvent, T _p = 20°C, 1 atm of ethylene gas, MAO as cocatalyst and Al/(CatA + CatB)) = 1000. ^b Determined by GPC at 150°C versus polystyrene standard.

^a13C nuclear magnetic resonance (400 MHz) spectra were obtained with o-C₆H₄Cl₂.

^b Percentage over total branching. ^c Number of branches per 1000 carbons.

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