Degradation And Stability Of Aliphatic Polyesters

Aliphatic polyesters, one of most promising biodegradable polymers, have been studied extensively and intensively due to their good biocompatibility and biodegradability, and they have found their applications in the fields of biomedical materials, drug delivery systems, packaging materials, agriculture, and so on.The thermal stability of aliphatic polyesters is very important to their processing and forming, specially for the aliphatic polyesters liable to thermal degradation such as poly(p-dioxanone) (PPDO). PPDO has good biocompatibility, biodegradability and mechanical properties, but it has a poor thermal stability. The ceiling temperature of polymerization of (p-dioxanone) (PDO) is only 265 ℃, much lower than that of L-lactide or ε-caprolactone. PPDO is usually synthesized through a ring-opening polymerization of PDO in the presence of organometallic catalyst such as SnOct₂, Al(OiPr)₃, and ZnEt₂. Due to the poor thermal stability, the molecular weight and melt viscosity of PPDO significantly decrease during processing, causing the deterioration of its mechanical properties. Therefore, how to enhance the thermal stability of PPDO is very important to the processing and extensive applications of PPDO.The properties and applications of aliphatic polyesters depended on their compositions and structures. The degradability is one of the significant factors affecting their applications. For example, poly(ε-caprolactone) (PCL) is suitable for implantation material, and not suitable for a carrier for fugitive drug due to its slow...