Synthesis and characterization of di- and triblock copolymers of poly(ethylene oxide) and poly(dl-valine-co-dl-leucine)

Di- and triblock copolymers of poly(ethylene oxide) (PEO) and poly(dl-valine-co-dl-leucine) were synthesized by ring-opening polymerization of N-carboxyanhydride (NCA)s of dl-valine and dl-leucine initiated by amine-terminated PEOs. The resulting block copolymers were characterized by 1H NMR, FT-IR, DSC, and wide-angle X-ray diffraction (WAXD). Differential scanning calorimeter revealed that the melting temperature of triblock copolymer was lower than that of diblock copolymer and the study of WAXD patterns of triblock copolymer indicated that PEO segments are stretched during the copolymerization as shown in the formation of complex. The self-assembly behaviors of these di- and triblock copolymers in the aqueous solution showed various forms.