ABSTRACT
This chapter discusses the properties of polyanhydrides before and during erosion and shows physicochemical ways of polyanhydride microsphere characterization. To understand the characteristics of polyanhydride microspheres, it is necessary to have a detailed knowledge of the properties of the polymers. Polyanhydrides have been investigated thoroughly during the last couple of years, which makes much physicochemical data available. Polyanhydrides are partially crystalline and, therefore, have a typical appearance under polarized light. The crystallinity of polyanhydrides can be adjusted through the copolymer composition. Important parameters for processing polyanhydrides to dosage forms are the glass transition temperature and the melting point. An understanding of polyanhydride erosion and degradation is essential to understand the properties of eroding polyanhydride microspheres. The techniques used for the characterization of polymer bulk erosion are also suited for the investigation of microspheres. An interesting approach to the reduction of organic solvent residues in polyanhydride microspheres is the formation of microspheres from melted polymer.
