Abstract
AbstractPolymer [ TiCl2, TiCl3, 3LiCl] complexes were used as solubilized Li/Ti(III) based initiators for Ziegler‐Natta polymerization of propene, leading to block copolymers. From measurements of the amount of diblock copolymers produced, a direct determination of the efficiency of the catalytic system was made. This efficiency was found to be equal to about 80% with respect to the number of potentially active centers. The activity of such systems was studied as a function of both initiator concentration and [monomer]0. From the measured values of activity and efficiency of the system, the rate constants of propagation were deduced. The kinetic behaviour of such a system is fully consistent with that of a living one. A first order kinetics towards both propene and active center concentration was found. Therefore, the rate constant of propagation is an absolute rate constant, measuring the intrinsic reactivity of active sites. GPC, 13C NMR and DSC analyses of the block copolymers permitted the establishment of their well‐defined linear diblock structure and disclosed a partial stereoregularity of the polypropene block (≈ 50% isotactic triads).
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