Synthesis and characterization of poly(ester amides)s with a variable ratio of branched odd diamide units

ABSTRACT The synthesis of a series of poly(ester amide)s constituted by glycolic acid, adipic acid, and different ratios of 1,3‐pentanediamine and 1,5‐pentanediamine units was studied and the derived copolymers were characterized. Thermal polycondensation between the potassium adipate salt and the appropriate ratio of N,N′‐bis(chloroacetyl)‐1,3‐pentanediamine and N,N′‐bis(chloroacetyl)‐1,5‐pentanediamine was proved to be effective, proceeded with high yield, and rendered samples with moderate molecular weight for carefully controlled competitive thermal degradation reactions. Physical properties were highly dependent on the final composition. In particular, crystallinity and thermal stability decreased with 1,3‐pentanediamine unit content, that is, with the incorporation of lateral ethyl groups into the main chain. The presence of these units also changed solubility in solvents like methanol and degradability in a protease K enzymatic medium. Specifically, incorporation of 1,3‐pentanediamine units led to a gradual increase in degradability. All poly(ester amide)s were able to establish intermolecular hydrogen bonding interactions, which in semicrystalline samples pointed to typical sheet structures of polyamides according to X‐ray diffraction and infrared spectroscopic data. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40102.