Cationic polymerizations of 1,3-pentadiene （PD） initiated by trimethylsilyl chloride （TMSCl） incombination with TiCl4 were carried out in n-hexane at 30℃. The yield of polymer was greatly increased bythe addition of TMSCl, indicating that the TMSCl/TiCl4 combination is an efficient initiating system for PDcationic polymerization. However, the introduction of TMSCl gave rise to a drop in the molecular weight ofthe polymer. Kinetic results demonstrated that the polymerization initiated by TMSCl/TiCl4 is 4.5 times fasterthan that induced by TiCl4 alone. Various ethers were used to mediate the TMSCl/TiCl4 initiating system.Adding diphenyl ether could increase both the yield and molecular weight of the polymer. Structural evidenceillustrates that the polymerization is indeed initiated by TiCl4 in combination with HCl resulting fromhydrolysis by adventitious water.
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