Hydrolytically Degradable Polymers as Biomaterials

Poly(a-ester)s, the most expansively studied class of biodegradable polymer, contain aliphatic ester linkages in their backbone which can be cleaved hydrolytically. It is reported that mere aliphatic polyesters with practically small aliphatic chains between ester bonds can decompose over the time needed for the majority of the biomedical applications. Poly(a-ester)s demonstrate enormous diversity and synthetic flexibility and, depending on the monomeric units, can be synthesized from a variety of monomers via condensation polymerization and ring-opening routes [19]. Poly(glycolic acid) and the stereoisomers of poly(lactic acid) are the most expansively investigated poly(a-ester)s polymers. 

Self-condensation of difunctional monomers such as diacid chlorides with diols, diacids with diols, hydroxy acids, or by the ester interchange reaction of diesters and 

Poly(L-lactide) is an ideal FDA approved polymer for biomedical applications because of slow-degrading characteristics and good tensile strength as compared to polyglycolide. The rate of degradation of poly(L-lactide) is very low and depends on the polymer crystallinity and the porosity of the matrix. Bulk erosion of the ester backbone via hydrolytic degradation generates lactic acid, which is broken down via the citric acid cycle into water and carbon dioxide [23]. 

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