Monoalkene Polymerization: Mechanisms

摘要: In spite of the intense research activity that has centred around Ziegler–Natta catalyst systems since their discovery in early 1950s, no definitive, unequivocal polymerization mechanism yet been devised to fully describe behaviour. One reason for this is complexity employed. For instance, itself may react as a solid or be soluble reaction medium; activation by an organometallic compound usually required but not always so; monomers are homo- co-polymerized gases liquids; electron donors added improve stereoregulation; and whole process performed under slurry, solution gas phase conditions. Since actual number propagating centres present on only small proportion total surface sites, it evident why direct spectroscopic studies structure have thus far limited value. Although developments NMR spectroscopy solids, EXAFS (extended X-ray absorption fine structure) SIMS (secondary ion mass spectroscopy) hold promise future, most evidence so reported scientific literature come from indirect kinetics, molecular weights weight distributions, polymer active centre concentrations.