The morphologies of a range of poly(ethylene oxide) diblock copolymers with polybutadiene (PB-PEO) and with polyisoprene (PI-PEO) were determined by small-angle X-ray scattering (SAXS) and some comparative studies were made by theology. These materials form micelles in water and the solutions give remarkably sharp SAXS patterns in which up to the sixth order reflection can be seen. The morphologies of two PEO diblocks formed from a commercial hydrogenated, mixed-architecture, polybutadiene (Kraton L1203(R)) have also been determined. Preliminary results are reported for a triblock copolymer poly(ethylene-alt-propylene)-polyethylene-PEO which has two crystallizable blocks.