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Polymerization of styrene with nickel complex/methylaluminoxane catalytic systems

✍ Scribed by Riccardo Po; Nicoletta Cardi; Roberto Santi; Anna Maria Romano; Carla Zannoni; Silvia Spera

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
122 KB
Volume
36
Category
Article
ISSN
0887-624X

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✦ Synopsis

Polymerization of styrene using catalytic systems based on nickel derivatives and methylaluminoxane (MAO) was studied. Among tested catalysts, nickel bis-(acetylacetonate) and nickel dichloride show the maximum activity. Bis(phosphine)nickel dichlorides exhibit lower activity, depending on the nature of the phosphine ligand. Polymer yields decrease by lowering the catalyst concentration, by increasing the reaction temperature, or by carrying out the polymerization in a polar donor solvent. Weight average molecular weight of most of the prepared polystyrenes ranges from 9000 to 25,000, with polydispersity indexes of 1.6-3.8. However, polystyrene prepared in dioxane solvent exhibits a small fraction of very high molecular weight (about 140,000). From NMR analysis, the products seem generally to be constituted of two polymers with different steric microstructure: atactic polystyrene and partially isotactic polystyrene (ca. 75-85% meso diads). Catalytic site specificity is correlated with the type of nickel ligand, while the effect of reaction temperature is less defined.

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