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Homopolymer Spatial Distribution in Blends with a Triblock Copolymer

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The spatial distribution of a homopolymer within the midblock microdomain of a triblock copolymer has been studied by the application of small-angle neutron scattering contrast matching techniques and small-angle x-ray scattering. These experiments are made possible by the use of a 1,2-butadiene precursor for the homopolymer and midblock, which may be modified by saturation with hydrogen, deuterium, or mixtures of the two in order to match the contrast of the polystyrene endblocks. If the contrast of the midblock and endblock sequences of the copolymer are matched, the spatial distribution of the homopolymer species dissolved within the midblock microdomain can be determined. The results demonstrate that the homopolymer prefers to reside preferentially in the center of the microdomain, in agreement with theoretical predictions, but that other morphologies are also present, probably due to non-equilibrium effects.