The Synthesis And Characterization Of Polyolefin-g-Polybutadiene Copolymers

Based on the coordination polymerization combining other polymerization techniques, to design and synthesis polyolefins with particular graft or block structures is the way for preparation of polyolefin copolymers with new topological structure.The thesis is dedicated to the synthesis of polyolefin-g/b-polybutadiene copolymers using Ziegler-Natta catalyst or rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2/dMAO catalyst. The polybutadiene in accurate molecular weight and microstructure which used in the coordination polymerization with Ziegler-Natta catalyst was synthesized by living anionic polymerization. Meanwhile, the (p-vinylbenzyl)polybutadiene macromonomers were also synthesized by living anionic polymerization which could be used to synthesize the PP-b-PB copolymers via a novel chain transfer reaction during metallocene-catalyzed propylene polymerization.Propylene ethylene and polybutadiene copolymerization using Ziegler-Natta catalyst or rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2/dMAO was examined. The obtained copolymers were characterized by1H-NMR and GPC and it showed that PP-g-PB、EP-g-PB copolymers were synthesized. The obtained copolymer depended on the polymerization conditions:For the Ziegler-Natta catalyst, with the increase of concentrations of PB or the decrease of the pressure of the polymerization, the polymerization activity gradually reduced and the molecular weight increased with a wider weight distribution at the same time. The polymerization system is more sensitive to the change of PB concentrations. What’s more, improving the content of1,2-structure of PB and increasing the ratio of ethylene could increase the PB insertion probability in copolymers and increase the conversion rate of1,2-structure. For the metallocene catalyst rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2/dMAO, a spot of PB could decrease the polymerization activity sharply and the molecular weight is low with a wide distribution.A series of (p-vinylbenzyl)polybutadiene macromonomers were synthesized by living anionic polymerization of butadiene followed by a direct coupling reaction of polybutadiyllithium with p-vinylbenzyl chloride. The control of the terminal functional groups is particularly important to ensure the reactivity of macromonomers. The experimental conditions were optimized to improve the percentage of the p-vinylbenzyl groups at the chain end. The macromonomers obtained were characterized by1H-NMR and GPC and it showed to be almost100%terminal functional groups with an excess of p-vinylbenzyl chloride ([VBC]/[PB’Li+]>8:1) at0℃in mixed solvent of THF and cyclohexane. The mechanism of the side reactions were also investigated.