The role of intermediate chain migration in propene polymerization using substituted {iPr(CpFlu)}ZrCl2/MAO catalysts

Site epimerization in ansa-zirconocene polymerization catalysts

“…If the enantioface selectivity is identical for the two sites (homotopic sites), the polymer produced is isotactic whereas syndiotactic polymer results if there is a preference for opposite propene enantiofaces, termed re and si [8], exerted by the two sites (enantiotopic sites). For stereorigid catalysts with sites exerting a clear chiral induction, qualitative prediction of the polymer microstructure may be relatively straightforward and based on symmetry considerations [9], and relatively simple, statistical models may, in fact, allow for a near-quantitative prediction of the polypropene microstructure [10,11].…”

Ethene Copolymerization with Trialkylsilyl Protected Polar Norbornene Derivates

“…Such an extended model, which has to be based on demanding theoretical calculations, should allow for a detailed description of the structure of the copolymer as it has been possible in the case of the propene homo-polymerization. [18] …”

“…The central part of the model structure (Zr, C a , O) is kept fixed in all subsequent calculations, while all other atom positions are optimized using the Tripos force field [15] and a special parameter set. [18] In Table 7 the energy differences DE 3-1-2 between the complexes of type 3 and the sum of the energies of the corresponding educts of type 1 and 2 are listed. Table 6.…”

13C NMR Studies of Ethene/Norbornene Copolymers using13C-Enriched Monomers: Signal Assignments of Copolymers Containing Norbornene Microblocks of up to a Length of Three Norbornene Units

“…[21] In addition, further investigations concerning the mechanism of the stereospecific insertion of the norbornene units will be carried out by using the results of this work through the performance of force field calculations which were successfully applied in propene polymerizations. [22] …”