| Abstract |
The recently reported N,N,N,N-tetradentate chelated alpha-diimine Ni(II) complexes 1-3 were demonstrated to be efficient precatalysts for the polymerization of styrene in the presence of MAO, producing isotactic-enriched heterotactic polystyrenes (isotactic contents in the range 73-75.5\%). The corresponding sequence distributions were determined by NMR spectroscopy, and fitted to six probabilistic models of chain propagation. A better conformity to a Bovey-first order Markov chain propagation model was obtained, indicating a chain-end control mechanism. A comparison of the microstructural features with other polystyrenes obtained by several different types of initiation indicates that the polystyrenes are formed by a coordination insertion polymerization mechanism at the nickel centers. (C) 2011 Elsevier Ltd. All rights reserved. |
