Polymerization of Styrene Versus Propylene with MgCl2-Supported Catalysts
It is well known that MgCl2-supported TiC14 (MgC12/TiC14) catalyst in combination with A1Et3 shows much higher activity in propylene polymerization than the conventional TiC13 catalyst system,1 but the stereospecificity of the obtained polymer is rather low, namely 20–40% as isotactic index (I.I.). In a study of kinetics on short time polymerization,2 it was concluded that a cause of the low stereospecificity of this catalyst system was due to the high concentration of atactic active centers ([C*]ata = 14–58%). We also reported that a catalyst system composed of MgC12/TiC14/ethyl benzoate- A1Et3/ethyl benzoate showed very high stereospecificity in both propylene and styrene polymerization and the concentration of the isotactic active centers in both polymerizations was similar,3,4 ([C*]iso(PP)) = 1.3%, [C*]iso(St) = 3%, suggesting comparable isotactic active centers for both monomers.
KeywordsCatalyst System Polymerization Time Methyl Ethyl Ketone Cationic Polymerization Styrene Polymerization
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