THEORY OF SUPERMOLECULAR STRUCTURES IN POLYDISPERSE BLOCK COPOLYMERS .4. CYLINDRICAL DOMAINS IN BINARY-MIXTURES OF DIBLOCK COPOLYMERS AND CYLINDER LAMELLAE TRANSITION

The theory of well defined superstructures formed in binary mixtures of diblock copolymers with different molecular weights and composition in a strong segregation limit has been developed. Three types of binary mixtures were considered: a mixture of two cylinder-forming block copolymers; a mixture of cylinder- and lamellae-forming block copolymers; and a mixture of two lamellae-forming block copolymers. The formation (conditions and the thermodynamic characteristics) of mixed lamellar and cylindrical superstructures and their thermodynamic stability were investigated. It was shown that in the case of non-isomorphous block copolymers the change in mixture composition leads to a first-order phase transition from one morphology of the superstructure to another, i.e. to real phase segregation (each phase remains microphase segregated). The theory was compared with experimental data. The possibility of the formation of cylindrical domains in the mixture of two lamellae-forming block copolymers was predicted.