|M.Sc Student||Smolensky Elena|
|Subject||Development of New Catalysts for Polymerization of Olefins|
|Department||Department of Chemistry||Supervisor||Professor Moris Eisen|
The development of new catalysts for the polymerization of olefins has been a great challenge due to the scientific and industrial importance. In the last two decades, the research has focused on developing novel catalysts that allow the control over the stereoregularity and concomitantly the physical properties of the obtained polymers. Furthermore, nowadays the plastic industry has a growing demand for new types of recyclable polymers exhibiting elastic properties. The research in this field is reaching a high level of sophistication, allowing already to connect between the symmetry of the complex and the stereoregularity of the produced polymer. For example, C2-symmetry complexes have been shown to produce stereoregular isotactic polypropylene, whereas C2v-symmetry complexes have been shown to induce the formation of atactic polypropylene.
The research presented here describes the synthesis and characterization of bis(diethylamine) titanium di-2-(diphenylphosphinoamido) pyridine complex designed to change symmetries during the polymerization reaction, towards the formation of an elastomeric polypropylene.
The titanium complex was reacted with MAO (methylalumoxane) forming a cationic complex, which is believed to be the responsible active species for the polymerization of propylene. Analysis of the cationic complex shows equilibrium between two different forms. The first species is a closed configuration with a pseudo C2-symmetry whereas the second species is an open structure with pseudo C2v-symmetry.
The cationic complex was tested for the polymerization of propylene. The polymer that was obtained in all the reactions was polypropylene with elastomeric properties. We can attribute such elastomeric properties to the equilibrium of the cationic complex. The isotactic domain will be formed when the cationic catalyst remains in its close configuration whereas the atactic domain will be formed when the complex is disposed in its open arrangement.
The physical properties of the polymer produced can be tuned by changing the ratio between the complex and the cocatalyst MAO, duration of the polymerization and solvent.