We report a synthetic method for the preparation of well-defined poly(styrene-b-butadiene) (PS-PB)(n), multiblock copolymers using a combination of living anionic polymerization and urethane based polycondensation along with an assessment of the associated microphase morphology and thermal and mechanical properties. The prepolymers, alpha,omega-dihydroxy polystyrene (HO-PS-OH) and alpha,omega-dihydroxy polybutadiene (HO-PB-OH), were prepared using a protected initiator, followed by deprotection and condensation with isophorone diisocyanate (IPDI) leading to the (PS-PB)(n) multiblock copolymers. Two types of block sequences were generated, one with random block sequences (PS-ran-PB)(n) and the second with alternating (PS-ran-PB)(n) block architectures. Size exclusion chromatography (SEC), H-1 nuclear magnetic resonance (NMR), and Fourier transform infrared spectrometry (FTIR) confirmed that the synthetic procedures yielded the desired products. Differential scanning calorimetry (DSC) revealed microphase separation and small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) demonstrated that the multiblock materials, containing between 69% and 85% by volume glassy PS, are characterized by a disordered bicontinuous-like morphology. Tensile tests demonstrated yielding followed by necking and an overall ductility that translates into much greater toughness than that typically found in glassy continuous SBS triblock copolymers.