Low-Dielectric Microcellular TLCP Composites Reinforced by Surface-Modified Hollow Glass Microspheres for High-Frequency Communications.

With the rapid development of high-frequency and high-speed communication technologies, there is an increasing demand for substrate materials that exhibit low dielectric constant, low dielectric loss, excellent mechanical performance, and high dimensional stability. Thermotropic liquid crystal polymers (TLCPs) stand out as potential candidates for these applications, attributed to their exceptional integrated performance profiles. To enhance hydrophobicity and interfacial compatibility within the TLCP matrix, silane coupling agent KH550 was employed to functionalize the surface of hollow glass microspheres (HGMs). Subsequent integration of the modified HGMs (M-HGMs) into TLCPs was achieved through melt blending, followed by the fabrication of reinforced TLCP foams via supercritical CO2 foaming. The results demonstrate that M-HGMs not only act as effective heterogeneous nucleation sites to refine the cellular structure of TLCP foams but also significantly enhance the interfacial adhesion with TLCPs. As a result, the compressive performance and dimensional stability of the TLCP foams are markedly improved, with the compressive strength reaching 1.68 MPa (an increase of 46.1%) and the coefficient of thermal expansion reduced to 69.9 ppm/°C (a reduction of 38.4%). Furthermore, the M-HGM-reinforced cellular TLCP composites demonstrate robust flame retardancy and exceptional dielectric properties, specifically a dielectric constant of 1.28 and a dielectric loss of 0.0004. Simulation results of patch antennas further confirm the feasibility and superiority of M-HGM-reinforced TLCP foam as an antenna substrate material for high-frequency communications, showing an improvement in signal transmission distance by more than one order of magnitude. This work offers a robust paradigm for engineering lightweight, high-performance TLCP foams tailored for next-generation high-frequency telecommunication infrastructures.