SYNTHESIS AND CONFORMATIONS OF A-B-A TRI-BLOCK COPOLYMERS WITH HYDROPHOBIC POLY(GAMMA-BENZYL L-GLUTAMATE) AND HYDROPHILIC POLY(ETHYLENE OXIDE)

Polymerization of gamma -benzyl N-carboxyl-L-glutamate anhydride was initiated by the primary amino groups capped at both ends of poly(ethylene oxide) as the middle block component. Before the preparation, the terminal hydroxyl groups of the middle block were reacted with excess tosylchloride. Subsequent treatment of tosylated poly(ethylene oxide) with potassium phthalimide and refluxing of the resulting product with hydrazine hydrate afforded the primary amine-terminated poly(ethylene oxide). From the data of infrared spectroscopy, it was found that the polypeptide chain block in A-B-A type block copolymers obtained exists in the alpha -helical conformation in the same manner as poly( gamma -benzyl L-glutamate).