OAPS-based PI aerogels used as antenna substrate in extreme environments

Abstract

Advances in high-frequency aerospace and communication systems require lightweight, low-permittivity, low-loss antenna substrates. While aerogels are promising due to their low density and dielectric constant, conventional polyimide (PI) aerogels suffer from high thermal expansion (CTE) and poor moisture resistance, resulting in interfacial delamination and dielectric instability. To address these challenges, octa-amino POSS (OAPS) was introduced as a crosslinking agent into the BPDA/PDA framework, fabricating a series of PI/OAPS hybrid aerogels. In this work, PI/OAPS aerogels with OAPS content ranging from 0.222% to 0.641% were prepared and showed excellent dielectric properties. Particularly at a content of 0.641% (corresponding to 20 repeating units), the aerogel achieved the lowest dielectric constant (Dk, 1.08 at 10.1 GHz) and dielectric loss (0.0013 at 10.1 GHz), which were reduced by 12.6% and 59.0%, respectively, compared with the unmodified aerogel. Furthermore, after the introduction of the OAPS, the contact angle of the PI/OAPS aerogel increased from 88° to 120°, and its coefficient of CTE was reduced to 16.7 ppm/K. Interestingly, antenna substrates fabricated from this material exhibited stable dielectric performance even when subjected to various extreme environmental tests, such as high-temperature aging (350℃), 85°C/85% RH aging, and thermal shock cycling with a temperature differential of 596°C. Therefore, this exceptional stability makes it an ideal candidate material for high-reliability, lightweight antenna substrates in extreme environments.