Role of tert ‐Butyl Methyl Ether (TBME) as an External Donor in Propene Polymerization with Dibutyl Phthalate (DBP)‐Containing MgCl 2 ‐Supported Ti Catalysts Activated with Al( i ‐C 4 H 9 ) 3

Stopped‐flow polymerization of propene was first conducted at 40 °C using the TiCl 4 /DBP/MgCl 2 catalyst (DBP = dibutyl phthalate) combined with Al(C 2 H 5 ) 3 . An induction period was observed at the beginning of polymerization, and the resulted polymer contained a considerable amount of the isolated ethylene unit. The formation of such unusual structures was concluded to be the result of copolymerization with ethylene originating from the ethylated Ti 4+ species. Catalyst washing with toluene and stopped‐flow polymerization at 70 °C brought about a drastic decrease in the contents of both Ti and DBP as well as a disappearance of both the induction period and isolated ethylene unit. The microstructures of polymers revealed that the highly stereoregular polymers are produced at the initial stage of polymerization. Changes in yield and molecular weight of polymers with polymerization time showed that the addition of tert ‐butyl methyl ether (TBME) brought about an increase in the concentration of active sites, but did not affect the propagation rate of propene polymerization. Such an increase in the active site concentration caused by an external donor has hardly been reported so far in kinetic studies using the stopped‐flow method; thus, the present result is believed to be a unique example. Kinetic curves of propene polymerization with the Cat. IV‐Al( i ‐C 4 H 9 ) 3 catalyst. (•): with TBME/Al = 0.1 and hydrogen, (♦): with TBME/Al = 0.1 and without hydrogen, (○): without TBME and with hydrogen, (⋄): without TBME and hydrogen. magnified image Kinetic curves of propene polymerization with the Cat. IV‐Al( i ‐C 4 H 9 ) 3 catalyst. (•): with TBME/Al = 0.1 and hydrogen, (♦): with TBME/Al = 0.1 and without hydrogen, (○): without TBME and with hydrogen, (⋄): without TBME and hydrogen.