Polymerization of styrene with nickel complex/methylaluminoxane catalytic systems

Abstract

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. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2119–2126, 1998

One-pot synthesis of isotactic-capped syndiotactic polystyrene with a bimetallic homogeneous catalytic system

“…Based on what it is known about the behavior of Ni(acac) 2 /MAO, 4 this last segment is likely to be isotactic (%mB70) and much shorter than the syndiotactic block: the lengths, estimated from the here-reported experimental meso diads content and typical meso diads content values found for iPS and sPS produced by Cp* catalysts, are about 5% of the syndiotactic block.…”

“…When they are combined, in principle, if the catalytic centers were independent the final products would be complex mixtures of polymers having different tacticities: sPS (afforded by titanium sites); iPS (afforded by nickel sites); and aPS (afforded by MAO and other non-stereospecific sites). As hot methyl ethyl ketone (MEK) dissolves aPS and iPS (up to %m¼90), 4 as well as the low-molecular-weight fraction of sPS, 14 extraction with MEK was applied to isolate the syndiotactic fraction for a better elucidation of the products structure. The results are reported in Table 2.…”

The syndiospecific polymerization of styrene in the presence of fluorine‐containing half‐sandwich metallocenes

“…Half-sandwich complexes of cyclopentadiene and substituted cyclopentadienes with titanium as the metal especially showed a high polymerization activity as well as a high proportion of syndiotactic polymer in combination with MAOs or boron organic compounds. [2][3][4] Although the cyclopentadienyl ring of the titanium compound has experienced a wide structure variation in the search for catalysts with a higher polymerization activity, much less attention has been paid to the variation of the other ligands of the metal cyclopentadienyl compound.…”

Morphology, Tensile Strength and Thermal Behavior of Isotactic Polypropylene/Syndiotactic Polystyrene Blends Compatibilized by SEBS Copolymers

“…[1][2][3][4] Syndiotactic polystyrene (sPS) is a new semicrystalline polymer with a melting temperature of about 270 C. Its high heat-resistance and modulus of elasticity, excellent resistance to chemicals and relatively fast crystallization rate make sPS a potential thermoplastic for a large number of applications in automotive and electronic industries. 5 It has gained increasing academic and industrial interests since its first successful synthesis using a metallocene catalyst as reported by Ishihara. 6 Despite these desirable properties, a disadvantage of sPS is its inherent brittleness.…”