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

Chain conformations of A-polymers of BAB two-component triblock and ABB gra ft 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 (N R). The middle A-block of BAB triblock copolymer has preferentially "loop" conformation when the Volume fraction. phi(A), of A-chain is high above 0.5 , while it does preferentially "bridge" conformation when phi(A) is low aro und 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 co polymer. The interfacial thickness of BAB triblock copolymer is almost cons tant irrespective of phi(A), and comparable with that of AB diblock copolym er. (C) 2000 Elsevier Science B.V. All rights reserved.