Polyurethanes from a system consisting of ethylene oxide endcapped poly(propylene oxide) polyol (PPO-EO), 4,4’-diphenylmethane diisocyanate (MDI) and ethylenediol (EDO) have been synthesized using a one-step process. The morphology of these polyurethanes has been investigated by a variety of techniques. Hard-segment-rich spherulites, with sizes of 10 mum in diameter, consisting of scattering fibrils, have been observed. The melting points of these spherulites lie in the range 220-260-degrees-C. The degree of microphase separation and the crystallinity of the polyurethanes increases with an increase in the hard-segment content. In addition, a relationship between the microstructure and the mechanical properties of these materials has been found.