THEORY OF TIME-DEPENDENT LOG-NORMAL MOLECULAR-WEIGHT DISTRIBUTION OF POLYOLEFINS IN HETEROGENEOUS ZIEGLER POLYMERIZATION

An explanation of the time-dependent log-normal molecular weight distribution of polyolefins in heterogeneous Ziegler polymerization is proposed on the basis of the non-uniformity of surface sites concerning the activation energy of the propagation reaction. It is a theoretical derivation of the Wesslau equation from the usual kinetic model. The theory explains the behavior of the molecular weight distribution, i.e., time and temperature dependences of polydispersity as well as large values of polydispersity in the early stages of polymerization, which have been observed experimentally.