AbstractThe kinetics of chain growth and chain transfer processes in the stereospecific polymerization of propylene, using catalytic systems such as TiCl3Al(C2H5)3and TiCl3AlCl(C2H5)2, has been examined. The number of active centers present on the catalyst surface has been determined radiochemically by kinetic and adsorption measurements, using aluminum labeled with C14. The mean life of macromolecules was determined by radiochemical determination of terminal groups, and the relationships between intrinsic viscosity and number‐average molecular weight were found. Kinetic research into ethylene‐propylene copolymerization enableld us to determine the different reactivity ratios of t