Tatsuya Shoji

Consideration of an activity of the metallocene catalyst by using molecular mechanics, molecular dynamics and QSAR

Abstract Recently metallocene based catalyst are widely used for the olefin polymerization catalyst. It is well known however that the metallocene catalysts do not show any activity without cocatalyst and also their activity depends on content and species of cocatalyst. In this study, the most stable structures of various catalyst–cocatalyst systems were calculated by using molecular mechanics (MM) and molecular dynamics (MD). Various structural parameters which are related to the space between central atoms of catalyst and cocatalyst, charges, and interaction energy were obtained from those structures. By using the quantitative activity–structure relationship (QSAR) analysis, the space between catalyst and cocatalyst was found to be the main factor to control the activity. By using this acknowledgment the activity of the metallocene catalyst may be roughly estimated without using the heavy ab initio molecular orbital calculation.

A simulation system for viscoelastic properties of polydisperse polymer melts

A simulation system is developed for evaluating viscoelastic properties of polymer melts with arbitrary polydispersity in molecular weight, starting from the known chemical structure of the polymers. The critical molecular weight for entanglement and molecular weight dependence of zero shear viscosity are evaluated based on theories of van Krevelen and Berry‐Fox by optimizing parameters associated with chain flexibility, chain length and effective molar weight per repeating unit. In the evaluation of viscoelastic properties of polymer melts, simple and reasonable shape of relaxation spectrum is assumed for polydisperse systems. Using molecular parameters evaluated above, frequency dependence of viscoelastic functions is calculated from the relaxation spectrum. This method is shown to be superior to the usual way of calculation of viscoelasticity based on blending rules: The time needed for the calculation is very short and does not depend on the polydispersity in molecular weight. Combination of the prese...