Bisphenol-Modified Ternary Liquid Crystal Polyarylates with Low Dielectric Loss at High Frequencies

Abstract

Thermotropic liquid crystalline polyarylates (TLCPs) with low dielectric loss at high frequencies have garnered significant attention due to their exceptional properties and high frequencies communication application. To investigate the influence of molecular structures on the dielectric constant and loss factor of TLCPs, 4,4′-dihydroxy diphenyl sulfone (SDP), 4,4′-dihydroxy diphenyl ether (ODP), 4,4′-dihydroxy diphenyl ketone (DHBP), and 4,4′-dihydroxy diphenyl sulfide (TDP) are introduced to copolymerize with 6-hydroxy-2-naphthoic acid (HNA) and terephthalic acid (TA) by one-pot melt polycondensation, which are defined as TLCP-I, TLCP-II, TLCP-III, and TLCP-IV, respectively. All prepared ternary TLCPs exhibit a nematic LC state between 300 and 350 °C, and the crystallinity of the modified TLCPs is reduced to a certain extent by introducing bisphenol moieties compared with the referenced polyarylate (TLCP-0) from 4-hydroxybenzoic acid (HBA) and HNA. Meanwhile, the consequent TLCPs exhibit good thermal stability, and the maximum weight loss rate temperature exceeds 500 °C. Furthermore, the initial storage modulus of TLCP-II, TLCP-III, and TLCP-IV films at room temperature are 1.2, 0.85, and 1.5 GPa, respectively, showing good tensile strength. Most importantly, the dielectric loss factors of TLCP-II, TLCP-III, and TLCP-IV are much less than 0.01 in the range of 1–10⁴ kHz, thus suggesting an ideal low-dielectric-material candidate.