Phenyl carbamate end-capped oligoesters: a model for hydrolytic stability of ester-based urethanes

A series of hydroxyl-terminated oligoesters were synthesized to determine the structural effects on the relative rates of hydrolysis in both acidic and alkaline media. Model compounds consisting of one diol and one dibasic acid were used because the simplicity of the chemical structure allowed for the analysis of individual effects. Linear, cycloaliphatic, and aromatic dibasic acids were used. The diacids were reacted with a series of linear and bulky diols. All hydroxyl-terminated oligoesters were end-capped with phenyl isocyanate. Three different stages were distinguished in the case of aliphatic oligoesters, while more bulky structures (cycloaliphatic and aromatics) only presented one or two stages. Hydrolysis rates showed a complex behavior where steric and anchimeric effects play a mutual role on initial hydrolysis rates.