Synthesis,characterization, and biodegradation of copolymers of unsaturated and saturated poly(ester amide)s

A new family of biodegradable copolymers of unsaturated poly(ester amide)s (UPEAs) and saturated poly(ester amide)s (SPEAs) based on L ‐phenylalanine, aliphatic dicarboxylic acids, and aliphatic dialcohols was synthesized by solution polycondensation and characterized. These unsaturated/saturated poly(ester amide) copolymers (USPEAs) were obtained in fairly good yields with N,N‐dimethylacetamide as the solvent. The molecular weights (M_n and M_w) of the USPEAs measured by GPC ranged from 15 to 60 kg/mol with a molecular weight distribution of 1.07–1.63. The chemical structures of the USPEAs were confirmed by both IR and NMR spectra. The USPEA copolymers had glass transition temperatures lower than that of pure UPEA but higher than that of pure SPEA. An increase in the unsaturated component in the USPEA copolymers led to an increase in their glass transition temperatures. The solubility of the copolymers was good in N,N‐dimethylacetamide and dimethyl sulfoxide but poor in water, acetone, methanol, and ethyl acetate. The preliminary in vitro biodegradation properties of the USPEA copolymers were investigated in both pure phosphate buffered saline (PBS) buffer and α‐chymotrypsin solutions. The copolymers showed significantly faster weight loss in an enzyme solution than in a pure PBS buffer. Upon the adjustment of the unsaturated‐to‐saturated diester monomer feed ratio, the obtained USPEA copolymers could have controlled chemical and physical properties, such as glass transition temperatures, solubility, and biodegradability, which could easily extend their applications to biomedical and pharmaceutical areas. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1595–1606, 2007