Polyurethanes containing various amounts of hard segment (HS) were synthesized with MDI, BD and PTMO of 1800g/mol molecular mass. The effects of HS content on the microphase separated structure and the deformation behavior were studied with FTIR, synchrotron SAXS and mechanical methods. It was found from the infrared dichroism method that the segmental orientation behavior was sensitively affected by the internal structure. Based on the dichroic results, a schematic model for the morphology of the segmented block copolymers containing different amounts of HS is suggested. As the HS content increases, the morphology changes from a soft-segment-continuous phase to a HS-continuous phas inversion was found to occur at around 50% HS content. The domain orientation and deformation behavior were also investigated with the synchrotron SAXS method. Using and one-dimensional detector and uniaxial stretcher, domains in which lamellae were oriented along the deformation direction were found to undergo expansion of the inter-domain spacing, i.e., d-spacing, at low draw ratio. As the draw ratio was increased further, the domain break-up and formation of new structure were observed for the polyurethanes of lower HS content. The mechanical stability of the hard domains was also found to increase with the HS content.