Abstract
The morphological behavior of a series of binary mixtures of polystyrene-block-polyisoprene (SI) diblock copolymers has been investigated by small-angle X-ray scattering and transmission electron microscopy. These mixtures consist of a given asymmetric SI diblock, coded as, which itself exhibits a morphology of polystyrene spheres on a body-centered-cubic lattice in a polyisoprene matrix and a symmetric SI diblock of lower molecular weight. This paper addresses the effect of varying the molecular weight of the symmetric diblock on the phase diagram of the binary blend. Three different short symmetric diblocks, coded s1, s2, and s3, have been used. Their molecular weights are such that both s1 and s2 are in an ordered state at room temperature, exhibiting the lamellar morpology, while the shortest one, s3, is in a disordered state. We show that over the whole composition range these binary mixtures do not undergo macrophase separation. The two types of chains self-organize in either a single ordered phase ...
Published Version
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