Synthetic Biodegradable Polymers for Medical Applications
This chapter presents the overview to elucidate the characteristics of several synthetic biodegradable polymers for medical applications, which include degradation modes and rates and their relationship to physicochemical, thermal, and mechanical properties. Synthetic biodegradable polymers mentioned in the chapter are poly (α-hydroxy esters), poly(ε-caprolactone), poly (ortho esters), polyanhydrides, poly(3-hydroxybutyrate) polyphosphazenes, polydioxanones, fumarate-based polymer, polyoxalates, poly(amino acids), and pseudopoly (amino acids). The stress/strain curves showing the effect of degradation on mechanical strength are given. Thermal and mechanical properties of the listed synthetic biodegradable polymers are tabulated. Some important types of polyphosphazenes that have been synthesized are nonhydrolyzable, hydrophobic polymers; nonhydrolyzable, hydrophilic polymers; and hydrolyzable polymers. Three types of fumarate-based polymers are discussed: 1) poly(propylene fumarate) (PPF), 2) poly(propylene fumarate-co-ethylene glycol) (P(PF-co-EG)), and 3) oligo(poly(ethylene glycol) fumarate) (OPF). Four important classes of polymers from dioxane-diones and oxalates are poly(1,4-dioxane-2,5-diones), polyoxalates, poly(1,3-dioxane-2-one) and poly(1,4-dioxane-2,3-dione), and poly(p-dioxanone). Pseudopoly(amino acids) are polymers derived from amino acids with nonamide linkages. The chemical structures of all the polymers are shown.