Copolymerization of ethylene and propene with a TiCl4/MgCl2‐Al(C2H5)3 catalyst system using a stopped‐flow method

Copolymerization of ethylene with a small amount of propene was conducted with a TiCl4/MgCl2‐Al(C2H5)3 catalyst system using a stopped‐flow method. With an increase in the polymerization time from 0,035 to 0,145 s, the copolymer yield increases linearly but the number‐average molecular weight of the copolymer showed a tendency of saturation. The rate constants of the propagation reaction as well as the concentrations of active sites were estimated using these data. On the other hand, the 1H NMR spectra of copolymer did not display the resonances due to CC double bonds which should be formed by chain transfer with monomer and/or by β‐hydrogen elimination. It was also found that the crystallinity of the copolymer decreases to a great extent upon incorporation of even a very small quantity of propylene units. From these results, it was concluded that the apparent rate of copolymerization is not controlled by monomer diffusion through the polymer films. Rather the transfer reaction with Al(C2H5)3 might predominantly take place during the copolymerization.