Homo- and co-polymerization of styrene with ethylene by novel nickel catalysts

• Published in: Polymer (Guilford) Vol. 42; no. 12; pp. 5069 - 5078
• Main Authors: Carlini, C, Galletti, A.M.Raspolli, Sbrana, G, Caretti, D
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.2001; Elsevier
• Subjects: Applied sciences; Copolymerization; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Preparation, kinetics, thermodynamics, mechanism and catalysts; Styrene polymerization; Styrene/ethylene copolymerization; Styrene/ethylene oligomerization; Styrene/ethylene copolymerization; Styrene polymerization; Styrene/ethylene oligomerization; Temperature effect; Complex catalyst polymerization; Complex catalyst; Experimental study; Complex catalyst copolymerization; Isotactic polymer; Ethylene copolymer; Reaction mechanism; Styrene polymer; Stereospecificity; Aluminium Organic compounds; Catalyst activity; Nickel II Complexes; Styrene copolymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(01)00002-7

The homopolymerization of styrene has been studied by using catalysts based on bis(α-nitroacetophenonate)Nickel(II) [Ni(naph) 2] and bis(hexafluoroacetylacetonate)Nickel(II) [Ni(hfacac) 2] precursors and methylalumoxane (MAO) as co-catalyst. The former system displayed at room temperature a higher activity as compared with other previously reported nickel catalysts, giving rise to a substantially atactic polystyrene with a quite low molecular weight. The use of the basic and bulky tricyclohexylphosphine (PCy 3) as ancillary ligand allowed to increase both molecular weight (∼20,000 Da) and isotacticity degree (∼50%) of the polymer. On the contrary, the use of the less basic triphenylphosphine (PPh 3) caused a reduction of isotacticity degree. On increasing the reaction temperature at 70°C, even in absence of the phosphine ligand, both catalytic systems gave a polymer characterized by about 50% isotacticity degree. A significant further increase of isotacticity degree (65–70%) was obtained when a AlMe 3 free MAO was adopted in combination with the above nickel precursors. The GC/MS analysis of the oligomeric products allowed us to conclude that styrene insertion is mainly of secondary type. The above catalytic systems were found also to copolymerize ethylene with styrene, giving rise mainly to oligomeric products.