Copolymerization Of Propylene And Unsaturated Aromatic Esters By Supported Ziegler-Natta Catalyst

The functionalization of polyolefin is always the attractive field of academic and industrial research. At present, there are three main approaches to synthesize functionalized polyolefin:post-functionalization of normal polyolefin, transform of reactive polyolefin intermediates, and direct copolymerization of olefin and polar monomer. Among them, the direct copolymerization is the most effective way. But the most difficult point is that the functional groups of polar monomer are easier to coordinate with active center than the double bond, resulting reduced activity or complete deactivation.Two long unsaturated aromatic esters of 2,6-diisopropylphenyl-10-undecylenate (DIPPU) and 2,6 -ditertbutyl-4-methylphenyl-10-undecylenate (DTBMPU) with big steric hindrance were synthesized and used to copolymerize with propylene. The result indicated that polar monomers could be copolymerized with propylene by supported Ziegler-Natta catalyst (TiCl4/MgCl2/AlEt3) if the functional group was shielded by the combination of steric hindrance and electronic effect. The copolymerization activities decreased with the increment of the concentration of polar monomer, but the decrement was not dramatic. Compared with DIPPU, DTBMPU presented the higher copolymerization activity due to its steric hindrance.Furthermore, the third polar monomer (UTIPB) was synthesized and used to copolymerize with propylene. The result indicated that UTIPB could be well copolymerized with propylene by supported Ziegler-Natta catalyst (TiCl4/MgCl2/ AlEt3) and the copolymerization activity is between those of DIPPU and DTBMPU. The influences of reaction temperature on the copolymerization were also investigated. As the temperature increased, the activity slightly decreased, and the amount of incorporated comonomer increased.The influence of polar monomer on copolymerization system was also studied. Four kinds of organic compounds, H-DIPPU, H-DTBMPU, DIPPA and DTBMPA, having the same functional groups as DIPPU、DTBMPU and UTIPB were synthesized In the presence of these compounds, the copolymerization activity of propylene and dodecene decreased, the average molecular weight and the isotacticity of copolymer increased, polydispersity index and the amount of increased commoner decreased. The facts indicate that these compound acts as external electron donor. Compared with propylene homopolymerization and copolymerization of propylene and dodecene, the copolymerization of propylene and polar comonomers showed low activities, and the copolymers had high molecular weight, and narrow molecular weight distribution, high isotacticity, low incorporated comonomer, and high Tm. It is concluded that the polar monomer performed as both reactive monomer and external electron donor.