Two series of segmented polyurethanes based on 3/2/1 and 2/1/1 molar ratios of methylene diphenyldiisocyanate (MDI), NN-bis(2-hydroxyethyl)isonicotinamide (BIN), and poly(tetramethylene oxide) (PTMO, MW = 1000) were synthesized and blended with different metal acetates. The thermal behavior and mechanical properties of the pyridine-containing polyurethane precursors and their blends were characterized by DSC, DMTA, and tensile testing. The results suggest that coordination between pyridine groups in the hard segments and the metal ions in the acetates improves hard-domain cohesion and phase separation and, subsequently, has an effect on mechanical properties. The varying ability of the pyridine group to coordinate with different cations results in different extents of phase separation. The interaction of pyridine with Ni or Cu (II) is much stronger than with Zn. It is shown that coordination interactions can be a driving force for phase separation and hard-domain aggregation in multiblock copolymer systems. Two different morphologies are proposed for polyurethanes of differing stoichiometry to explain the differences in the results from DMTA and tensile testing.