Morphology and micromechanical deformation behavior of styrene-butadiene block copolymers. IV. Structure-property correlation in binary block copolymer blends

The structure-property correlation in blends consisting of styrene/butadiene block copolymers forming alternating polystyrene (PS) and polybutadiene (PB) lamellae, and PS domains in rubbery matrix was investigated by different microscopic techniques (transmission electron microscopy, scanning force microscopy, and scanning electron microscopy), uniaxial tensile testing, and dynamic mechanical analysis. Unlike the pure lamellar block copolymer, the blends showed predominantly disordered wormlike morphology formed by the intermolecular mixing. These structures allowed a precise control of stiffness/toughness ratio of the blends over a wide range. The blends showed a gradual transition from predominantly viscoplastic to elastomeric behavior with increasing triblock copolymer content. The results demonstrated that the binary block copolymer blends provide the unique possibility of tailoring mechanical properties on the basis of nanostructured polymeric materials. (C) 2004 Wiley Periodicals, Inc.