High-Performance Segmented Liquid Crystalline Copolyesters

The ability of a multiphase copolymer to exhibit both the physical properties of liquid crystalline and elastomeric polymers enables a variety of emerging applications. Traditional synthetic methods often require many steps to achieve such diversity in a copolymer. This work describes the synthesis and characterization of biphenyl-containing segmented copolyesters in a single step. A fundamental investigation of the thermal and thermomechanical properties as a function of methylene spacer length demonstrates a relationship between melting temperature and even/odd spacer lengths. DSC and SAXS analysis reveal microphase separation in these randomly segmented copolyesters. The copolymers retain a liquid crystalline morphology despite the incorporation of a flexible oligomeric polyether, and melting and isotropic temperatures ranged from 77 to 167 °C and 117 to 217 °C, respectively. Wide angle X-ray diffraction provides further insight into the effect of the soft segment on the highly crystalline nature of the segmented copolyesters. Thermomechanical analysis and tensile testing elucidate the effect of hard segment (HS) content and structure. Plateau moduli range from ≈5 to 150 MPa and increasing from 50 to 75 wt% HS doubled tensile strain. This synergy will enable superior fabrication and processing of intricate electronic devices that require high-thermal properties and mechanical durability. One-pot melt transesterification affords a novel series of Pluronic-containing segmented liquid crystalline copolyesters. Systematically changing the methylene spacer and soft segment oligoether elucidates structure-property-morphology relationships for tailoring to high-performance applications.