Linear/branched Block Polyethylene Produced by a-Diimine Nickel(Ⅱ)Catalyst and Bis(phenoxy-imine)Zirconium Binary Catalyst System in the Presence of Diethyl Zinc

In order to promote development of linear/branched block polyethylenes based on new catalytic systems,we synthesized a novel a.dimine nickel(Ⅱ)complex with isopropyl substituents on ortho-N-aryl and hydroxymethyl phenyl substituents on para-Naryl structures.The activity of a-dimine nickl(Ⅱ)catalyst was 3.02x10^(6)g-mol_(ni)^(-1)·h^(-1) at 70℃,and resultant polyethylene possessed 135/1000C branches.The linear/branched block polyethylenes were synthesized from ethylene polymerization catalyzed by the a-dimine nicke(Ⅱ)complex/bis(phenoxy-imine)zirconium in the presence of diethyI zinc.With the addition of ZnEtz(from 0 to 400),the melting peak of resultant polyethylene changed from a single melting peak to bimodal melting peaks.The molecular weights of resultant polyethylene ranging from 26.8 kg/mol to 17.1 kg/mol and PDI values varying gradually from 24.4 to 15.2 were obtained vla adjusting ZnEt;equiv.and molar ratio of two catalysts.In addition,the branching degree of the polyethylene increased from 13/1000C to 56/1000 with the increase of the proportion of a dimine nickel(Ⅱ)catalyst.Using this binary catalyst system,the reaction temperature of chain shutting polymerization can be carried out at 70℃,which is more conducive to industrial application.

Highly Active New α-Diimine Nickel Catalyst for Polymerization of Ethylene

A new α-diimine ligand 1a, bis[N,N′-（4-tert-butyl-2,6-dimethylphenyl）imino]-2,3-butanediylidene and its corresponding Ni（II） complex 2a, {bis[N,N′-（4-tert-butyl-2,6-dimethylphenyl）imino]-2,3-butanediylidene}dibromo- nickel were successfully synthesized, and characterized by 1H NMR, 13C NMR, Fourier transform infrared spectroscope（FTIR）, elemental analysis and X-ray photoelectron spectroscopy（XPS）. α-Diimine ligand 1b, bis[N,N′-（2,6- dimethylphenyl）imino]-2,3-butanediylidene and its corresponding Ni（II） complex 2b, {bis[N,N′-（2,6-dimethyl- phenyl）imino]-2,3-butanediylidene}dibromonickel were also synthesized and characterized for comparison. The pre-catalyst 2a with sterically bulky, electron-donating group tert-butyl, activated by diethylaluminum chloride （DEAC） and tested in the polymerization of ethylene, was very highly active[2.01×107 g PE/（mol Ni？h？0.1 MPa）] and led to a very highly branched polyethylene（ca. 35―103 branches/1000 C）. The state of the polyethylene obtained varied from plastic, elastomer polymers to the oil-like hyperbranched polymers.

SYNTHESIS OF BIMODAL POLYETHYLENE WITH UNSYMMETRICAL α-DIIMINE NICKEL COMPLEXES: INFLUENCE OF LIGAND BACKBONE AND UNSYM-SUBSTITUTED ANILINE MOIETY

A series of unsymmetrical a-diimine nickel complexes with various backbones and substituted aniline moieties were synthesized and characterized. The crystallographic analysis of the nickel complexes confirmed the existence of meso-and rac-configuration in solid structure. Nickel complexes after activation by MAO were screened for ethylene polymerization to evaluate backbone substituent effect on synthesis of bimodal PE. Acenaphthyl nickel complex with planar backbone afforded a bimodal PE with a broad polydispersity, whereas camphyl nickel complex with rigid and bulky backbone afforded a monomodal PE with a narrow polydispersity. Steric effect of aniline moiety for acenaphthyl nickel complex was also examined, and bimodal PE with dominant high-molecular-weight fraction was obtained by modifying substituents on aniline moiety.

POLYMERIZATION OF 1-OCTENE AND DETERMINATION OF MARKHOUWINK CONSTANTS OF POLY(1-OCTENE)

The polymerization of 1-octene initiated by methylalmnoxane （MAO）-activated Ni（II）-based-a-diimine complexes [（2,6-i-Pr）2C6H3-DAB（An）]NiBr2 was investigated. Using this catalyst, poly（1-octene）s with molecular weight between 100 × 10^3 and 400 ×10^3 and polydispersity （Mw/Mn） between 1.3 and 1.5 were synthesized successfully by varying reaction time at room temperature. The poly（1-octene）s were amorphous polymers and could be well soluble in tetrahydrofuran （THF）. After fractional precipitation, poly（1-octene）s with narrow molecular weight distributions （Mw/Mn 〈 1.12） were obtained. Their weight-average molecular weights were measured by gel permeation chromatography （GPC） in conjunction with online model BI-MwA multiangle laser light scattering （MALLS）, and their intrinsic viscosities were measured by Maron＇s single-point method. The k and a values in Mark-Houwink equation [η] = KM^a in THF at 40α were 0.089 mL/g and 0.61 respectively.