Tacticity control of polypropylene using a C2-symmetric family of catalysts
A family of C2-symmetric catalysts was designed and synthesized with the
intent to polymerize propylene. The catalyst was designed to be C2-symmetric for the
specific goal that the catalyst would have two identical sites for the propagation of
the polymer and therefore eliminate some of the stereoerrors that occur in the
propagation of the polymer chain. This catalyst would also operate under simple
enantiomorphic site control and therefore the insertion of the monomer would be
governed by the ligand surrounding the active site. The ligands were synthesized
with increasing degrees of steric bulk with the intention to determine if a catalyst
system could generate elastomeric polypropylene.
Enantiomorphic site control polypropylene utilizes statistical methods to
determine the Si and Re content of a given polymer chain as a function of the
variable E. Polypropylene samples generated by the catalyst family were analyzed
using high temperature pentad analysis of the methyl region to calculate the E value.
The goal was to observe E to be equal to 0.78 provided that the number molecular
weight of the polymer was 100,000. The catalyst systems generated polymers with values higher and lower than the desired 0.78, indicating too high or too low
enantioselectivity of the catalyst systems respectively at Tp = 0Â°C.
Advisor:Miller, Stephen A.; Bergbreiter, David E.; Grunlan, Jaime C.
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Date of Publication:12/01/2007