Processing and hydrolytic degradation of aromatic, ortho-substituted polyanhydrides

Abstract

Polyanhydrides containing 1,3-bis(p-carboxyphenoxy)propane, abbreviated poly(p-CPP), are currently being used as controlled-release devices for the treatment of brain cancer. These polymers are biodegradable and biocompatible and release pharmaceuticals in a controlled fashion. However, polyanhydrides have an important drawback: The polymers themselves are highly insoluble in both organic solvents and water and have high melting temperatures, rendering them difficult to process into fibers and/or films. Previously, we synthesized polymers that overcame the solubility and, thus, processing problems associated with poly(p-CPP). In this report, we describe the mechanical properties and hydrolytic degradation characteristics of these newly developed polyanhydrides. After formation of films by either compression-molding or solvent-casting, the polymer surfaces were examined by SEM. Mechanical studies were also performed on the compression-molded samples. Compression-molded samples were sterilized by γ-irradiation and then examined by GPC for changes in their polymer structure. Lastly, the polymers and the degradation media were evaluated by TGA, DSC, GPC, and HPLC to gain a better understanding of the degradation process.