AbstractCopolymers and alternating block copolymers were prepared both containing a liquid crystalline (LC) polyether segment, based on 4,4′‐biphenyldiol(3)and 1,5‐dibromopentane(2), and a thermoplastic segment, deriving from an aromatic poly(ether sulfone) (PSU)(1). The alternating block copolymer was prepared by the phase transfer catalyzed (PTC) polyetherification of mesogenic α,ω‐bis(5‐bromopentoxy)polyether(5)with α,ω‐bis(hydroxyphenyl)PSU(1). Copolymers containing mesogenic segments were prepared utilizing α,ω‐bis(hydroxyphenyl)‐PSU as another diphenol in the PTC polyetherification of5with2and3. The thermal behavior, as characterized by differential scanning calorimetry (DSC), revealed phase separation for all prepared copolymers as well as liquid crystalline behavior down to a content of mesogenic units deriving from5as low as 30 wt.‐%. Optical polarization microscopy, however, revealed significant differences in textures of the copolymers with the textures observed for homopolymer5. Textures of a5/PSU blend clearl