SYNTHESIS AND STRUCTURAL STUDY OF AN ABA BLOCK-COPOLYMER CONSISTING OF POLY(EPSILON-BENZYLOXYCARBONYL-L-LYSINE) AS THE A-BLOCK AND POLY(ETHYLENE OXIDE) AS THE B-BLOCK

ABA-type block copolymers composed of poly(epsilon-benzyloxycarbonyl-L -lysine) (PCLL) as the A component and poly(ethylene oxide) as the B c omponent were synthesized by polymerization of epsilon-benzyloxycarbon yl-L-lysine N-carboxyanhydride initiated by primary amino groups locat ed at both ends of the PEO chain. From circular dichroism measurements in solution, as well as from infrared spectra measurements in the sol id state, it was found that the polypeptide block exists in the alpha- helical conformation, as in PCLL homopolymer. The intensity of wide-an gle X-ray diffraction patterns of the block copolymers depends on the PEO content and shows basically similar reflections as the PCLL homopo lymer. The morphology examined by transmission electron microscopy and differential scanning calorimetry revealed microphase-separated struc ture.