We have synthesized SC-LCPUs from 1,1'-methylenebis(4-isocyanatobenzene) (MDI) and azobenzene mesogenic diols (alpha-[bis(2-hydroxyethyl)amino]-omega-(4-R-azobenzene-4'-oxy)alkanes, R = -OCH3, -CN and -NO2) with 4, 8 or 12 methylene spacer units. All the C4RMDIP are amorphous polymers showing no mesomorphic properties, whereas for C8RMDIP polyurethanes only C8OMeMDIP is liquid-crystalline. The smectic structures of C12RMDIP polymers are defined by the terminal group; the layer spacing values give the order CN>NO2>OMe.