Interfacial structures of block and graft copolymers with lamellar microphase-separated structures

Abstract

Chain conformations of A-polymers of BAB two-component triblock and ABB graft copolymers, composed of polystyrene (=A) and poly(2-vinylpyridine) (=B), with lamellar microphase-separated structures were investigated by small-angle neutron scattering (SANS), and interfacial thicknesses of AB diblock and BAB triblock copolymers were compared by using neutron reflectivity (NR). The middle A-block of BAB triblock copolymer has preferentially “loop” conformation when the volume fraction, φ A, of A-chain is high above 0.5, while it does preferentially “bridge” conformation when φ A is low around 0.3. A-graft chain of ABB copolymer has slightly larger dimension along the direction parallel to lamellar interface than A-chain of AB diblock copolymer. The interfacial thickness of BAB triblock copolymer is almost constant irrespective of φ A, and comparable with that of AB diblock copolymer.