Two prototype triblock (ABA) copolymers of poly[(γ-benzyl- l-glutamate) x (butadiene/acrylonitrile) y (γ-benzyl- l-glutamate) x] have been synthesized and characterized. They were prepared by reacting a primary amine capped butadiene/acrylonitrile (ATBN) polymer with the N- carboxy anhydride of γ-benzyl- l-glutamate. The copolymers were ∼38 000 (copolymer 1) and 74 000 (copolymer II) molecular weight. X-ray diffraction and Fourier Transform infrared spectroscopy of films cast from dioxane (preferential for PBLG) and chloroform (non-preferential) show the benzyl glutamate segments to be predominantly α-helical and disordered α-helical, respectively. Electron microscopy of osmium tetroxide strained films cast from dioxane revealed lamellar domain formation indicative of phase separation. The midblock butadiene layers were ∼150 Å thick while the alternating benzyl glutamate layers were 300 and 500 Å thick for copolymers I and II, respectively. Films cast from chloroform exhibit a nearly homogeneous morphology, indicative of considerable phase mixing. Dynamic mechanical spectroscopy of the copolymers also revealed a dependence on morphology. The side chain transition of the benzyl glutamate appeared as a single peak when the copolymers were cast from dioxane and a double peak when the copolymers were cast from chloroform.