| 초록 |
The mechanism of regioselectivity in styrene polymerization with ansa-metallocene catalyst was investigated using the density functional theory (DFT). In order to study the regioselectivity in the stage of initiation of polymerization, the DFT calculations were performed for primary and secondary insertions of the first styrene monomer into an activated catalyst, i.e., SiH2Cp2Ti+-CH3 (Cp = η5-C5H5). The results reveal that primary insertion leads to a product structure blocking additional monomer insertions, whereas secondary insertion yields a product appropriate for successive monomer insertions. We also study the case of region-irregular chain propagation and compare the energy profiles with that of regio-regular chain propagation. From these energy analyses it is found that the repulsive interactions between phenyl rings of monomers and ligand of catalyst play a crucial role in the regioselectivity during chain propagation. |
