Branched thermotropic liquid crystal polymer with favourable processability and dielectric properties

Thermotropic Liquid Crystal Polymer (TLCP) has emerged as a promising material for 5G mm-wave antennas due to its low dielectric constant and loss at high frequencies. However, its low melt viscosity, inadequate melt elasticity, and rigid rod-like macromolecular chain with easy orientation pose a significant challenge in the production of isotropic films. In this study, in order to improve the melt viscosity and melt elasticity of TLCP, a multifunctional epoxide-based branching agent (ADR 4468) was applied to produce branched TLCP. The impact of the branched structure on linear viscoelastic, thermal, mechanical, and dielectric performance was investi-gated. Results from linear rheological characterizations indicated that complex viscosity and storage modulus of modified TLCP samples were significantly enhanced, indicating the presence of long-chain branches. The me-chanical performance of modified samples was scarcely affected by the concentration of ADR 4468, with a tensile strength of approximately 245 MPa, and Charpy notched impact strength of approximately 30 KJ/m2. However, with an increase in ADR 4468 content, the dielectric constant increased (from 3.25 to 3.30 at 10 GHz) as well as the dielectric loss (from 1.36 x 10-3 to 2.14 x 10-3 at 10 GHz). Based on the overall performance, the optimal content of ADR 4468 was found to be about 2-3 wt%. These findings offer insights into the potential applications of modified TLCPs as substrates for 5G mm-wave antennas.