Control of branch formation in ethylene polymerization by a [Ni(eta3-2-MeC3H4)(diimine)] PF6 / DEAC catalyst system

Fernanda F N Escher,Roberto F De Souza,Raquel S Mauler

doi:10.1590/s0103-50532001000100006

Fernanda F N Escher, Roberto F De Souza + Show 1 more

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https://doi.org/10.1590/s0103-50532001000100006

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Abstract

The polymerization of ethylene mediated by [Ni(eta³-2-MeC3H4){ArN=C(H)C(H)=NAr}] PF6, Ar = 2,6-C6H3iPr2 /DEAC catalyst precursor under mild reaction conditions (reaction temperature between -10 ºC and 25 ºC and ethylene pressure between 109 and 1520 kPa) yields high molecular weight branched polyethylene. The degree of branching was modulated by a careful choice of reaction conditions. Thus, at 0 ºC and 109 kPa, the branching degree was 17 branches/1000 backbone carbon atoms and at 25 ºC, it went up to 90 branches/1000 backbone carbon atoms. The nature of the observed branches (methyl, ethyl and longer), their quantity and distribution along the polymer backbone chain can be rationalized in terms of a chain walking process and control of the extend of isomerization by the steric hindrance of the growing chain.

Highlights

Nickel-diimine complexes have been extensively described[1,2] and claimed to be catalysts in the Du Pont de Nemours’s Versipol process[3]
We described previously that cationic nickel η3-allyldiimine complexes are able to polymerize ethylene even when associated with low amounts of diethylaluminum chloride (DEAC)[11].The polyethylenes obtained in such processes have shown variable degrees of branching[12]
In this work we describe the tailoring of branching by the control of the reaction conditions, allowing access to new materials with different branch distributions along the polymer chain

Summary

Introduction

Nickel-diimine complexes have been extensively described[1,2] and claimed to be catalysts in the Du Pont de Nemours’s Versipol process[3]. We described previously that cationic nickel η3-allyldiimine complexes are able to polymerize ethylene even when associated with low amounts of diethylaluminum chloride (DEAC)[11].The polyethylenes obtained in such processes have shown variable degrees of branching[12].

Results

Conclusion