Summary: Novel polyurethane elastomers (PUs) were synthesized with ethylene glycol (EG) as a chain extender. The macrodiol was poly(ethylene adipate) (PEA), MW = 2000 ± 50. Two isocyanates were employed: 4,4′-methylene bis(phenyl isocyanate) (MDI) and 4,4′-dibenzyl diisocyanate (DBDI). The conformational mobility of DBDI causes an unusually wide range of mechanical, physical and chemical properties, associated with the possibility of pronounced phase separation into a domain – matrix morphology, and with a higher tendency to crystallization and self-association by hydrogen bonding. Materials were characterized by wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical analyses (DMA), and mechanical measurements. Results were discussed in terms of the effect of PUs crystallinity. In the case where the chain extender–diisocyanate couple was EG-DBDI, the hard segments were observed to crystallize. The DBDI based PUs displayed higher flow stress in the hard phase caused by stronger phase segregation.