Copolymerization of ethylene with ω-p-methylpenyl-α-olefin using Et(Ind)2ZrCl2/MAO as a catalyst

Modification of polyethylene with polar groups and/or polar polymer side chains has been an issue for both academic and industry fields for a long time. Many method have been presented to prepare functional polyethylene, among which the post-functional method has find its industry applications. However, this method shows many disadvantages in controlling polymer structure. The reactive monomer method is characterized by good control of polymer chain structure. We have prepared an ethylene/p-allyltoluene copolymer by Et (Ind)(2)ZrCl2/MAO. This copolymer can be transferred to polyethylene graft copolymers using graft-from technique from the site of benzyl groups. In this paper, copolymerization of ethylene with three kinds of omega-p-methylphenyl-alpha-olefins, p-methylphenyl-propylene (AC(3)), 4-p-methylphenyl-1-butene (BC4) and 6-p-methylphenyl-1-hexene (HC6) using Et (Ind)(2)ZrCl2/MAO as a catalyst was performed in order to compare the copolymerization abilities of the three reactive comonomers. Three comonomers were synthesized by the coupling reactions between benzyl or aryl metal (magnesium or lithium) and alkenyl halide. The comonomers were purified to get the polymerization grade. Ethylene/reactive comonomer copolymerization was carried out under 1.01 x 10(5) Pa of ethylene with variations of the comonomer quality in the feed. The copolymers were characterized with H-1-NMR, C-13-NMR, GPC and DSC. With the feed of comonomers the catalyst activity increased, reached a maximum value and then decreased. Under the same concentration of comonomers, the highest catalyst activity occurred in the BC4 system. The content of comonomer in copolymers increased with the comonomer in the feed. Under the same concentration of comonomers, the content of comonomer in copolymers could be used to compare the copolymerization ability of the comonomers. The examination results showed that the best copolymerization ability came from BC4. With the increase of the content of comonomer in copolymers, the melting point of copolymers decreases, and the peak in DCS curves becomes broad. This is because the incorporation of comonomers destroyed the crystal of polyethylene. The incorporation of comonomers in copolymers caused a decrease in polymer molecular weight. The possible reason was that more beta-H chain transfer reactions were induced by the comonomer. Three kinds of copolymers were characterized with H-1-and C-13-NMR, all of the H and C atoms could be found in their NMR spectra. And no evidence proved that two comonomer molecules were connected directly. The above results showed that BC, was a favorable comonomer which had the best incorporation ability.