Effect of Solvents on Living Polymerization of Propylene with [t‐BuNSiMe2Flu]TiMe2‐MMAO Catalyst System

Abstract

AbstractSummary: Batchwise polymerization of propylene was conducted at 0 °C in heptane using [tert‐BuNSiMe2Flu]TiMe2 (1) combined with dried methylaluminoxane (MAO) and dried modified methylaluminoxane (MMAO), which were prepared from the toluene solutions of MAO and MMAO by removing the solvent and the free trialkylaluminium. The dried MMAO system quantitatively gave the polymer with higher molecular weight and narrower molecular weight distribution (MWD), ca. 1.3, compared with the dried MAO system. In addition, the polymerization with dried MMAO in toluene, chlorobenzene (CB) and ortho‐dichlorobenzene (o‐DCB), as solvent, also produced polymers quantitatively with MWD of ca. 1.1–1.3. The number‐average molecular weight ($\overline M _{\rm n}$) of the polymers, obtained with these systems, increased linearly against the polymer yield, while the narrow MWD was retained and the number of polymer chains was almost constant. The results of post‐polymerization in heptane and o‐DCB proved that the living polymerization proceeded irrespective of the solvent used. The semi‐batch polymerizations under an atmospheric pressure of propylene indicated that the propagation rate was more than 10 times higher in o‐DCB than in heptane. The 13C NMR analysis of the polymers indicated that the syndiotacticity also depended on the polarity of the solvent and increased in the following order: CB ≤ o‐DCB < toluene < heptane.A plausible scheme for the interaction between active species and solvents.imageA plausible scheme for the interaction between active species and solvents.