| Abstract
| - Blends of poly(styrene)-b-poly(isoprene) (PS−PI) and poly(isoprene)-b-poly(ethylene oxide)(PI−PEO) were investigated by small-angle X-ray scattering, photon correlation spectroscopy, lightmicroscopy, and rheology. Blends were prepared in which both diblocks had the same PI composition, f,and were investigated as a function of blend composition, Φ. We generally found a disordered one-phaseregion at high temperatures and two macrophase-separated, ordered phases at low temperatures. Atlow temperatures the only appreciable miscibility was found for f = 0.7 in the PI−PEO-rich phase. Atintermediate temperatures we generally observed macrophase separation before microphase separationupon cooling. The macrophase separation boundary compared to the microphase boundary is loweredupon increasing f. For f = 0.6 and 0.7 we observe an adjustment of the d spacing of the macrophase-separated, ordered phases. The general trend of the phase behavior is described by a theory using therandom phase approximation.
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