Amorphous segmented polyurethanes (PUs) were prepared by a solution two-step synthesis from 2,4-toluenediisocyanate, 1,4-butanediol and ATBN, a telechelic butadiene-acrylonitrile oligomer. The composition was varied in the range 11-61% by wt of ATBN. The copolymers were characterized by elemental analysis, viscosity measurements and FTIR and H-1-NMR spectroscopy. Differential scanning calorimetry and dynamic mechanical thermal analysis showed the presence of two separate glass transitions for hard and soft segments, thus indicating a two phase behaviour of the investigated PUs. Evidence of interphase interactions was not found. The dynamic mechanical spectra suggested the occurrance of a phase inversion from a hard segment matrix to a soft segment continuous phase when the ATBN content is 38% by wt or higher.