Temperature-Invariant Large Broadband Polyimide Dielectrics with Multimodal Porous Networks

초록

Herein, we describe sponge-like polymeric materials withmultimodalporous networks with stable ultralow dielectric properties over broadfrequency and temperature ranges. A hierarchically porous polyimide(PI) film was prepared via nonsolvent-induced phase separation (NIPS),followed by stepwise thermal imidization. Through the swelling andthe subsequent liquid-liquid phase separation, highly insulatinginterconnected pores of the internal layer and the water-vapor impermeable,closed-cell skin of the outer layer were directly formed on the PIfilm. The grafting of porous PI onto amino-functionalized mesoporoussilica (AMS) to further adjust the overall thermal stability and dielectricconstant has become a valid strategy. The porous PI-grafted-AMS (PPI-g-AMS) exhibited uniform micropores, which were regularlyshaped with an average diameter of 16.3 +/- 0.6 mu m. The glasstransition temperature (T (g)) of PPI-g-AMS increased considerably from 367 degrees C to as highas 398 degrees C because of the formation of interchain cross-linkingbridges in the AMS. Outstanding dielectric constant (D (k)) and dissipation factor (D (f)) of 1.84 and 0.0018 at a frequency of 1 MHz, respectively, wereachieved for PPI-g-AMS-1 with the addition of AMSwith 1% wt. Moreover, stable and ultralow D (k) (similar to 1.84 at 1 MHz) and D (f) (similar to 0.001at 1 MHz) values were achieved over a broad temperature range from-20 to 200 degrees C. These findings indicate the broad applicationpotential of polymeric materials as interlevel insulation materialsin the next-generation 5G/6G infrastructure.

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