Synthesis, characterization, and biodegradation of novel poly(ether ester amide)s based on L-phenylalanine and oligoethylene glycol

A new family of novel biodegradable poly(ether ester amide)s (PEEAs) consisting of three building blocks (L-phenylalanine, oligoethylene glycol, and aliphatic acid dichloride) were synthesized by solution polycondensation. Using N,N-dimethylacetamide as the solvent, these PEEA polymers were obtained with fairly good yields with reduced viscosity (eta(red)) ranging from 0.13 to 0.61 dL/g. The chemical structures of the PEEAs were confirmed by IR, NMR spectra, and elemental analysis. The PEEAs had Tg values lower than that of the saturated poly(ester amide)s (PEAs) of similar structures due to the incorporation of ether bonds in the backbones. An increase in the number of ether bonds in PEEA resulted in a lower Tg value. The solubility of the PEEA polymers in a wide range of common organic solvents was significantly improved when compared with unsaturated PEAs. The preliminary in vitro biodegradation behaviors of PEEA polymers were investigated in both pure PBS buffer and alpha-chymotrypsin solution of different concentrations. The polymers showed a significantly faster weight loss in an enzyme solution (alpha-chymotrypsin) but a very slow biodegradation rate in pure PBS buffer. The enzymatic hydrolysis rates of PEEAs (in terms of weight loss) were found to be much faster than those of saturated and unsaturated polyesteramides reported in previous studies. The zero-order-like biodegradation kinetics and molecular weight data also suggested surface erosion biodegradation mechanisms for these PEEAs.