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A-B-A type tri-block copolymers composed of e-N-benzyloxycarbonyl-L-lysine as the A component and butadiene as the B component were prepared. The synthesis could be carried out by allowing the N-carboxy anhydride of the a-amino acid to react with the amineterminated polybutadiene. The structure of these block copolymers was estimated using the relation between the helix-coil transition temperature and the number-average molecular weight. The morphology of the membrane specimens was investigated by wide-angle X-ray diffraction and electron microscopy. It was found that the dynamic mechanical spectra can be well explained by the microheterophase structure observed under electron microscope. By minimizing the Gibbs free energy /'lG per unit volume for the micelle formation, the domain size was estimated for each type of micelle. The shape and size calculated were in accord with those observed by electron microscope. KEY WORDS Tri-Block Copolymer I Poly(e-N-benzyloxycarbonyl-Llysine) I Poly butadiene I Microheterophase Structure I Dynamic Mechanical Properties I

The mechanical properties of and the hydraulic permeability of water toward membranes of A-B-A tri-block copolymers consisting of a-helical poly(y-benzyl L-glutamate) as the A-component and poly butadiene as the B-component, were examined and compared with the same properties of poly(y-benzyl L-glutamate) membrane. Analysis of the temperature dependence of the dynamic modulus and the loss modulus based on Takayanagi's mechanical model leads to the conclusion that the dynamic mechanical spectra can be well explained by the micro-heterophase structure observed by electron microscope. The hydraulic permeability K of water for the block copolymer membranes is dramatically higher than that of homopolypeptide, and increases in proportion to the interfacial are<: between the A and B domains. This fact suggests that the residues near the end of polypeptide chain and the terminal residues of amine-terminated poly butadiene, which locate in the interfacial region between the a-helical A-component and the B-component, are responsible for the water permeability, since NH and CO residues in this region do not form intramolecular hydrogen bonds. KEY WORDS Tri-Block Copolymer I Poly(y-benzyl L-glutamate) I Polybutadiene I Mechanical Properties I Water Permeability I

A-B-A tri-block copolymers consisting of DL-isomers of poly(y-methyl glutamate) as the A component and polybutadiene as the B component were prepared. The synthesis was carried out by polymerizing an equimolar mixture of y-methyl D-glutamate and y-methyl Lglutamate NCA with the amine groups capped at both ends of the polybutadiene block or the initiator. By infrared spectroscopy, it was found that the copolypeptide chain block exists not only in an ()(-helical conformation but also in a random coli conformation. On the basis of contact angle measurements, replication electron micrographs, and attenuated total reflection-infrared spectra, it was concluded that the surface of the present block copoly.mer membranes has a microheterophase structure consisting of the copolypeptide and hydrophobic domains, and also has a grainy surface structure with a grain size of 300-500 A. Furthermore, the adsorption of plasma proteins onto these block copolymer membranes was investigated.