A quantum chemical study on polymerization catalysts for polyesters: Catalytic performance of chelated complexes of titanium

In this study, we performed quantum chemical calculations on the electronic state, steric structure, polycondensation and thermal degradation catalytic activities of titanium(IV) model catalysts with multidentate ligands. Activation energies for polycondensation and thermal degradation reactions catalyzed by model catalysts indicated that activation energies for both reactions were in positive correlation. Nevertheless, principal component analysis on electronic structure descriptors of model catalysts exhibited that a titanium(IV) complex with large 2nd principal component could be a good catalyst with high polycondensation and low degradation activities. Finally, we examined titanium(IV)-sugar alcohol complexes which meet the condition of 2nd principal component. Since they gave relatively low activation energies for polycondensation and high ones for thermal degradation, we were convinced that they should be promising candidates of non-antimony polycondensation catalysts. Moreover, sugar-alcohol catalysts are thought not to cause polymer coloration because TDDFT calculation gave no significant absorbance in visible region for them.