Effect of electron donors on 1,3-butadiene polymerization by a Ziegler-Natta catalyst based on neodymium

High-cis polybutadiene produced by catalyst systems based on a rare earth is an elastomer used to produce green tires. This type of tire presents lower rolling resistance, which allows higher fuel economy, and thus fewer chemical compounds are discharged into the atmosphere. In this work, the influence of electron donors [tetrahydrofuran (THF) and tetramethylethylenediamine (TMEDA)] present in the polymerization solvent on the microstructure and molecular weight characteristics of the polybutadiene produced by neodymium catalysts was studied. The catalyst synthesis was carried out in glass bottles for I h at a temperature between 5 and 10 degrees C. The catalyst components were diisobutylaluminum hydride, neodymium versatate, and tert-butyl chloride. The polymerization reaction was carried out for 2 h. The reaction temperature was kept at 70 +/- 3 degrees C. The addition of TMEDA or THF above a determined concentration reduced the catalytic activity, molecular weight, and concentration of cis-1,4 units (<96%), whereas the polydispersity increased. (c) 2005 Wiley Periodicals, Inc.