Block copolymers polybutadiene/poly(benzyl‐L‐glutamate) and polybutadiene/poly(N⁵‐hydroxypropylglutamine) preparation and structural study by X‐ray and electron microscopy

AB block copolymers with an amorphous polybutadiene block and a polypeptide block were prepared. The method of synthesis consists in the preparation of a polybutadiene block by anionic polymerization followed by a chemical modification of its living end introducing a primary amine group which is able to intiate the polymerization of the N ‐carboxy anhydride (NCA) of the chosen amino acid. By this way the block copolymers polybutadiene/poly(γ‐benzyl L‐glutamate) ( 14a ) were prepared, in which the poly(γ‐benzyl‐ L ‐glutamate) block could be transformed into a poly( N 5 ‐hydroxypropyl‐ L ‐glutamine) block by reaction with 3‐amino‐1‐propanol leading to the block copolymers polybutadiene/poly( N 5 ‐hydroxypropylglutamine) ( 14b ). By using X‐ray diffraction and electron microscopy it could be shown that the block copolymers 14a and 14b exhibit mesophases in different solvents and it was established that the structure of the mesophases is lamellar. Each sheet of the lamellar structure consists of the superposition of two layers: one formed by the polybutadiene chains in a more or less random coil conformation; the other formed by the polypeptide chains in an α‐helix conformation, arranged in an hexagonal array and folded.