Lifetime of growing polymer chain in stopped-flow propene polymerization using pre-treated Ziegler catalysts

The lifetime of a growing polymer chain of monoester-type and diester-type supported catalysis was investigated by the stopped-flow polymerization technique. A linear correlation of the polymerization time with both the polymer yield and the molecular weight was observed for the monoester-type supported catalyst until a certain time period (0.2 s), where the growing polymer chain is still active. The activity of the diester-type supported catalyst was found to increase gradually throughout the polymerizations (0-1.2 s). The polymer yield and the molecular weight are proportional to time up to 1.2 s when the pre-treatment of the diester-type supported catalyst was conducted with triethylaluminium. The active sites on the pre-treated catalyst exert a longer lifetime (at least 1.2 s) compared with that on the monoester-type supported catalysts without pre-treatment. Kinetic studies indicated that the pre-treatment influences not only the number of active sites, but also the ratio of isospecific active sites to aspecific ones formed on the supported catalyst.