Dicyclopentadienyl complexes of titanium,niobium, and tungsten in the controlled synthesis of poly(methyl methacrylate)

Organometallic compounds Cp₂TiCl₂, (EtC₅H₄)₂NbCl₂, and (PrⁱC₅H₄)₂WCl₂ were assessed as additives that control polymer chain growth in the polymerization of methyl methacrylate. In the presence of compounds mentioned in amounts comparable with that of the initiator, a uniform process with no gel-effect occured and respective linear increase in the molecular weight of the polymer up to high degrees of the monomer conversion was observed.     

Tricarbonylchromium complexes of styrenes in radical copolymerization

The organometallic monomers styrenetricarbonylchromium and p‐methylstyrenetricarbonylchromium were copolymerized in ethyl acetate solutions with methyl methacrylate and butyl acrylate using azobisisobutyronitrile at 50 °C and a binary system including di‐tert‐butylperoxytriphenylantimony at 30 °C as the free‐radical initiators. Comonomers are proposed to form a molecular complex based on the results of ultraviolet and electron spin resonance spectroscopy. A kinetic study shows that chromium‐containing monomers at high concentrations in the mixture reduce the rate of copolymerization. The addition of styrenetricarbonylchromium to butyl acrylate significantly slows down the autoacceleration. The reactivity ratios of the comonomer pairs, namely, styrenetricarbonylchromium–methyl methacrylate, styrenetricarbonylchromium–butyl acrylate and p‐methylstyrenetricarbonylchromium–methyl methacrylate, were determined using the method of Kelen–Tudos for low conversion polymerizations.Copyright © 2001 John Wiley & Sons, Ltd.     

Vinylarenetricarbonyl complexes of chromium as chain propagation regulators for polymerization of acrylic monomers

The polymerization of methyl methacrylate and butyl acrylate initiated by azo‐bis‐isobutyronitrile in the presence of metal‐containing monomers (p‐methylstyrene‐, stilbene‐ and α‐methylstyrene‐chromiumtricarbonyl) was studied. Kinetic parameters (i.e. the decrease in the autoacceleration during the polymerization of acrylic monomers, its shift towards a high conversion region in the presence of α‐methylstyrenechromiumtricarbonyl, a linear dependence of the molecular weight of a polymethyl methacrylate and the shift of molecular‐weight distribution curves to a high molecular weight region with conversion) demonstrate the influence of vinylarenetricarbonyl complexes of chromium on basic steps of polymerization. It is important to note that the above organometallic compounds enable the controlled synthesis of polymers under temperature conditions (50–70 °C) corresponding to those of the industrial polymer production. Copyright © 2003 John Wiley & Sons, Ltd.     

Diphenylbutadiene chromium tricarbonyl in radical polymerization of methylmethacrylate

The synthesis of poly(methylmethacrylate) in the presence of diphenylbutadiene chromium tricarbonyl under radical initiation and temperature conditions that approach those in industry proceeds without autoacceleration and is characterized by a linear increase in the polymer molecular weight with conversion. Copyright © 2005 John Wiley & Sons, Ltd.