The higher activation energies of A3 and A4 suggest a new reaction mechanism: perhaps the Lewis acidity of [gamma]-alumina starts to dominate the cure of BECy.
Besides the adsorbed water and hydroxyl groups on the surface contributing to the cure of BECy, the electron donating character (Lewis acidity) of the [gamma]-alumina, appears to significantly affect the cure kinetics.
The catalytic activities of the zinc carboxylates were understood with considering electronic natures and steric hinderances of substituents, Lewis acidity of the centered zinc metal, and morphological changes.
Thus, the keto-linkage causes a decrease in the nucleophilicity of carboxylates of GA, consequently affecting the Lewis acidity of the centered zinc metal ion which plays as the active site to copolymerize [CO.sub.2] and PO monomers.
Thus, the substituted keto-linkage affects more severely the carboxylic acid group nearest to the 2-carbon than the other carboxylic acid, consequently influencing Lewis acidity of the zinc metal ion in the catalyst.
These substituents may affect Lewis acidity of the centered zinc metal ion as well as morphology in ZnO/GA catalyst.