Poly polyanhydride chain

Polyanhydrides with hydrophobic fatty acid terminals have been reported (Teomim and Domb, 2001) as shown in Scheme 5.4. In this reaction, SA was polymerised with acetic anhydride to form prepolymer of poly(sebacic anhydride) (PSA). It was hydro-phobised by the interchange of polyanhydride chain with previously prepared fatty acid anhydrides of acetic acid. 

Polyanhydrides have been modified by incorporating amino acids into im-ide bonds. The imide with the terminal carboxylic acids is activated with acetic anhydride and copolymerized with sebacic acid or CCP. Poly(anhydride-imides) increase the mechanical properties of the polyanhydrides. Degradation of poly(anhydride-imide)s is similar to that of polyanhydrides (i.e., surface erosion). Two different cleavable bonds (anhydride and ester) in the polymer chains have been included in polyanhydrides. Carboxylic acid-terminated e-caprolactone oligomers or carboxylic acid-terminated monomers (e.g., salicylic acid) have been polymerized with activated monomers (e.g., SA). 

Polyanhydrides are characterized by anhydride bonds connecting monomers along the chain, or by anhydride groups located on the side of the chain and not along the backbone. Indeed, poly (malic anhydride) is a polyethylene chain with anhydride groups as side chains (Fig. 1.10). 

Acid labile moieties inside polyanhydrides, poly(lactic/glycolic acid) (PLGA), and poly(b-amino esters) (PbAEs) induce redox responsiveness. Another typical redox-responsive pol mier is poly(NiPAAm-co-Ru(bpy)3), which can generate a chemical wave by the periodic redox change of Ru(bpy)3 into an oxidized state of lighter color. This redox reaction alters the hydrophobic and the hydrophilic properties of the potymer chains and results in swelling and deswelling of the potymer [103]. 

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