The synthesis and some thermal and dynamic mechanical properties of four series of liquid-crystalline block copolymers, comprising polystyrene and polyester blocks, are described. Within each series, the smectic C-nematic and nematic-isotropic transition temperatures of the polyester block were constant throughout the whole composition range, and the enthalpies of both phase transitions were directly proportional to the composition. The two blocks were incompatible in the glass and melt phases and underwent their individual phase transitions.