(CH3)(3)SiCl/TiCl4 initiating system for cationic polymerization of 1,3-pentadiene

Cationic polymerizations of 1.3-pentadiene (PD) initiated by trimethylsilyl chloride (TMSCl) in combination with TiCl4 were carried out in n-hexane at 30 degrees C. The yield of polymer was greatly increased by the addition o f TMSCl, indicating that the TMSCl/TiCl4 combination is an efficient initia ting system for PD cationic polymerization. However, the introduction of TM SCl gave rise to a drop in the molecular weight of the polymer. Kinetic res ults demonstrated that the polymerization initiated by TMSCl/TiCl4 is 4.5 t imes faster than that induced by TiCl4 alone. Various ethers were used to m ediate the TMSCl/TiCl4 initiating system. Adding diphenyl ether could incre ase both the yield and molecular weight of the polymer. Structural evidence illustrates that the polymerization is indeed initiated by TiCl4 in combin ation with HCl resulting from hydrolysis by adventitious water.