Abstract:

The branched polyethylene(br-PE) were synthesized by [ArNC(An)-C(An)NAr]NiBr₂[An=acenaphthyl, Ar=2,6-C₆H₃(^emPr)₂] in the presence of the modified methylaluminoxane(MMAO) and methylaluminoxane(MAO). The effects of experimental conditions in which ethylene pressure, temperature and time were varied on ethylene polymerization were investigated. The structures of the obtained polyethylene were characterized by high-temperature NMR, high-temperature GPC and DSC. It was found that the activities from MMAO were higher than that from MAO about 10 times, which reaches 10⁷ g/(mol Ni·h). The branches of polyethylene prepared from MMAO were about (45-64)/1000C, while that from MAO were about (82-88)/1000C. The mechanical properties of the br-PE were analyzed and compared with low density polyethylene(LDPE) and ethylene propylene methylene(EPM). It was shown that br-PE exhibits high tensile strength(27.90 MPa), which is much higher than LDPE(14.40 MPa) and EPM(5.44 MPa). The elastic modulus of br-PE is 2.10 MPa, almost same as EPM(2.11 MPa). The elongation at break of br-PE is 774.6%, little higher than that of LDPE(725.6%), but lower than that of EPM(1770.1%).)

Key words: Late transition metal catalyst, α-Diimine nickel complex, Ethylene polymerization, Branched polyethylene