Structural modification, hydrolytic degradation

Polyanhydride structures can be modified by the addition of aminoacids, linked via imide bonds at the amino terminus, so that the carboxylic acid terminus remains available for the interaction with acetic anhydride [459]. These poly(anhydride-imides) degrade in a similar way as the simple polyanhydride polymers. Other modifications that can take place are copolymers linked with esters. In that way, the polymer contains two types of hydrolytically cleavable bonds. In the presence of water, both types of bonds are hydrolyzed, releasing the dicarboxylic acid and the ester [460]. An example of a poly(anhydride-ester) with application in the medicinal field includes sebacic acid and salicylic acid, a therapeutically useful compound. The release of sebacic acid in the body opens up a variety of potential applications. 

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