Low dielectric constant dielectrics possess a broad prospect for application in microelectronic devices. The most efficient method for fabricating low dielectric constant dielectrics is the incorporation of pores into the materials. However, the introduced pores simultaneously decrease the mechanical properties of the dielectrics, which limits further application of these materials. Herein, we report the fabrication of polyarylene ether nitrile (PEN) foams possessing ultralow dielectric constants and excellent mechanical properties via delayed phase inversion method. Scanning electron microscopy (SEM) observations indicate that the porous structure of PEN foams is composed of finger-like pores and cellular pores. Due to the existence of these pores, the density of the PEN foams is as low as 0.158 g∙cm^-3, and the homologous void fraction is up to 87.5%. As a result of the high void fraction, the PEN foam demonstrates an ultralow dielectric constant of 1.25 at 1 kHz. On the other hand, deriving from the high performance nature of the PEN, the PEN foams reveal excellent mechanical properties with a specific modulus up to 1027 MPa∙cm³∙g^-1 and an elongation at break higher than 22%; additionally, these foams are flexible enough to be folded repeatedly without fracture. The simultaneous achievement of ultralow dielectric properties and excellent mechanical performances intensify the competitiveness of PEN foams for applications in microelectronic devices.

低介电常数电介质在微电子器件中具有广阔的应用前景。制造低介电常数电介质的最有效方法是在材料中掺入孔。然而，引入的孔同时降低了电介质的机械性能，这限制了这些材料的进一步应用。本文中，我们通过延迟相转化法报道了具有超低介电常数和优异机械性能的聚亚芳基醚腈（PEN）泡沫的制备。扫描电子显微镜（SEM）观察表明，PEN泡沫的多孔结构由手指状的孔和细胞孔组成。由于这些孔的存在，PEN泡沫的密度低至0.158 g∙cm ^-3，并且同源空隙率高达87.5％。由于高的空隙率，PEN泡沫在1 kHz时具有1.25的超低介电常数。另一方面，由于PEN的高性能，PEN泡沫具有优异的机械性能，比模量高达1027 MPa∙cm ³ ∙g ^-1，断裂伸长率高于22％；此外，这些泡沫具有足够的柔韧性，可以反复折叠而不会破裂。同时实现超低介电性能和出色的机械性能，增强了PEN泡沫在微电子设备中的应用竞争力。