Polymerization of higher α‐olefins using a C_s‐symmetry hafnium metallocene catalyst. Kinetics of the polymerization and microstructural analysis

Abstract

The C s -symmetry hafnium metallocene [(p-Et 3 Si)C 6 H 4 ] 2 C(2,7-di-tert-BuFlu) (C 5 H 4 )Hf(CH 3 ) 2 and tetrakis(pentafluorophenyl) borate dimethylanilinium salt ([B(C 6 F 5 ) 4 ] À [Me 2 NHPh] þ ) were used as the catalytic system for the polymerization of higher a-olefins (from hexene-1 to hexadecene-1) in toluene at 0 C. The evolution of the polymerization was studied regarding the variation of the molecular weight, molecular weight distribution and yield with time. The effect of the monomer structure on the polymerization kinetics was established. The role of trioctylaluminum in accelerating the polymerization was investigated. 13 C NMR spectroscopy was used to study the microstructure of the poly(a-olefins) by the determination of the pentad monomer sequences. The thermal properties of the polymers were obtained by differential scanning calorimetry, DSC. The results were discussed in connection with the polymer microstructure.

Preparation of ultra high molecular weight amorphous poly(1-hexene) by a Ziegler-Natta catalyst

“…[1,2,18,21] The polymerization activity increased with increasing monomer concentration. It may be a result of higher access of active catalyst centers to the monomers that leads to increase of propagation rate compared with the chain transfer and deactivation reactions.…”

“…[26] The crystallization of the polymer chains was prevented by the steric hindrance induced by the side groups. [2] Vortex test for estimating DRA efficiency…”

Synthesis and characterization of iPP‐sPP stereoblock produced by a binary metallocene system

“…The effect of MAO vs. MAO + BHT on chain shuttling by Al was investigated. 6(e) , Longer Al alkyls have also been explored …”

Bis(β‐enaminoketonato) vanadium (III or IV) complexes as catalysts for olefin polymerization

“…The advance of homogeneous metallocene catalysis in the past two decades has allowed chemists to make significant progress in understanding the relationship between structure and activity in olefin polymerizations. [1][2][3][4] This significant achievement has stimulated many researchers to develop nonmetallocene catalysts based on both early and late transition metals which have led to extraordinary advances in producing polyolefin in a precise controlled macromolecular architecture. [5][6][7][8][9] New catalysts for olefin polymerization play a critically important role in the development of new materials as well as in upgrading the performance of existing polyolefins.…”

“…69,70 The family of neutral, single-component, late transition metal olefin polymerization catalysts bearing monoaniomic N,O-ligands have been reported and exhibited activities toward ethylene polymerization and cycloolefins (co)polymerization. [71][72][73] We recently reported that salicylaldiminato vanadium(III) complexes (see Scheme 1) were efficient catalysts for ethylene polymerization in the presence of Et 2 AlCl and Cl 3 CCOOEt, the structural model of the salicylaldiminato vanadium(III) complexes greatly affected the ethylene polymerization behaviors, and found that the bis(salicylaldiminato) vanadium(III) catalysts displayed higher thermal stability than the corresponding vanadium(III) catalysts bearing single salicylaldiminato ligand. 74 As catalyst optimization has been achieved primarily by varying the N-moiety and aryloxy moiety of the phenoxyimine ligand, we decided to study the influence of conjugate effect on the backbone of the N,O-chelating ligands on catalyst performance.…”