Testing DFT ability to predict the stereoselectivity of group 4 metallocenes in propylene polymerization
Journal Title: Polyolefins Journal - Year 2014, Vol 1, Issue 2
Abstract
In this study we have tested the ability of a standard DFT computational protocol to reproduce the experimentally obtained stereoselectivity of 26 different C2-symmetric zirconocene catalysts active in propylene polymerization. The catalysts were chosen for their relevance in metallocene catalyzed polymerization of propylene. To this end, primary insertion of both si- and re-propylene enantiofaces into the Zr-CH2-CH(CH3)2 bond was considered to simulate the growing chains step. The energy difference between these two transition states, ΔEre-si, was taken as a measure of the stereoselectivity (pentad: mmmm%) of different catalysts. The results clearly indicated that there was a good agreement between ΔEre-si and the mmmm% values, so that greater ΔEre-si could correspond to higher mmmm%. A model was fitted to the experimentally obtained mmmm% against theoretical ΔEre-si. The coefficient of determination (R2) of the resultant plot was 0.9793, which indicated a good accuracy of the model. Finally, to quantify the steric role of the studied ligands in the observed stereoselectivity, the analysis of the buried volume (VBur) and of the steric maps was performed for two representative complexes. The images revealed that a greater asymmetric localization of the %VBur around the metal center led to a higher mmmm% in the resultant polymer.
Authors and Affiliations
Naeimeh bahri-Laleh, Laura Falivene, Luigi Cavallo
Keywords
Related Articles
- EP ID EP283078
- DOI 10.22063/POJ.2014.1100
- Views 122
- Downloads 0
Preparation and characterization of polyethylene/ glass fiber composite membrane prepared via thermally induced phase separation method
Grinded glass fiber (GGF) embedded high density polyethylene (HDPE) membranes were prepared via thermally induced phase separation method. FESEM images showed that all the membranes had leafy structure, indicating a soli...
Synthesis and identifcation of polystyrene via conventional and controlled radical polymerization methods: Effect of temperature, initiator and transfer agent on molecular weight and reaction rate
Polystyrene (PSt) has been known as one of the important polymers with a wide range of applications. Ability to synthesize PSt with different but predictable molecular weights for various applications is very important i...
Effect of NH3/methylaluminoxane/dodecylamine modifiednanoclay on morphology and properties of polyethylene/ clay nanocomposites prepared by in-situ polymerization
This study presents methods for treating a kind of nanoclay and investigates the effects of methylaluminoxane (MAO) exposure time and or dodecylamine (DDA) reflux time on in-situ polymerization of ethylene in the presenc...
Expected nucleation effects of carboxylic acid salts on poly(1-butene)
9,10-Dihydro-9,10-ethano-anthracene-11,12-dicarboxylic acid disodium salt (DHEAS) was synthesized and used as a nucleating agent for poly(1-butene) (iPB). The isothermal crystallization kinetics of iPB having different n...
Polymerization of sterically hindered a-olefins with singlesite group 4 metal catalyst precursors
A variety of group 4 metal catalytic systems (C2-symmetric {EBTHI}-, {SBI}-type zirconocene complexes (C2-1–4); C1-symmetric (C1-5–8) and Cs-symmetric (Cs-9) {Cp/Flu}-type zirconocene complexes; Cp*2ZrCl2 (Cp* 2-10)), ha...