Optimization and regulation of alcohol-based co-foaming agents on foaming behavior of ultra-low dielectric constant polyarylene ether nitrile foam in supercritical CO2

The incorporation of high porosity can effectively mitigate the dielectric constant and dielectric loss of polymers, thereby satisfying the stringent demands of ultra-low dielectric constant materials (ultra-low k < 2.0) in high-frequency and high-speed communication networks. In order to effectively enhance the foaming ability of the polyarylene ether nitrile (PEN), alcohol-based co-foaming agents with different chain lengths were introduced to fabricated high expansion ratio PEN foam using supercritical carbon dioxide foaming technology. By regulating and optimizing foaming temperature, type and content of co-foaming agents, the foaming window of PEN foam can be expanded by 20 °C while achieving a maximum expansion ratio (R) of up to 6.7. PEN foam achieves the preparation of materials with ultra-low k, with a minimum dielectric constant and dielectric loss of only 1.26 and 0.0025, respectively. The results obtained from fitting the theoretical model indicate that, for PEN foams with a porosity exceeding 80 % (R > 5.0), both the Bruggeman equation and the Clausius-Mossotti equation closely approximated the measured values. Additionally, PEN foam exhibits excellent thermal stability (Td5 > 445.8 °C) due to the "physical shielding" effect provided by cells. These advancements contribute to enhancing competitiveness of PEN foam with ultra-low k in for modern communication fields.