Precise Synthesis and Liquid Crystallinity of Poly(Alkylene 4,4'‐bibenzoate)‐Based Oligomers and Alternating Copolyesters

Poly(alkylene 4,4'‐bibenzoate)s ( BB‐ n ), a class of semi‐flexible main‐chain thermotropic liquid‐crystalline polyesters (TLCPs), exhibit well‐defined and thermally stable smectic A or C A phases and have therefore been widely investigated. BB‐ n are typically synthesized via polycondensation of 4,4'‐bibenzoate and diols; however, precise control over molecular weight and molecular sequence remains challenging, hindering the development of well‐defined oligomers and sequence‐controlled copolymers. Herein, we precisely synthesized BB‐ n ‐based dimers, trimers, and alternating copolymers via Suzuki–Miyaura cross coupling reaction, and their LC properties were systematically evaluated. While the BB‐ n dimers and trimers did not exhibit any LC phases, alternating copolymers—composed of pentylene and hexylene or 2,2,3,3,4,4‐tetrafluoropentylene spacers—formed higher‐ordered smectic‐like phases with lower isotropization temperatures compared to the corresponding BB‐ n . This study demonstrates that spacer‐sequence engineering is an effective molecular design and opens new possibilities for structural and morphological control in BB‐ n type TLCPs.