Synthesis and characterization of flexible and high temperature resistant polyimide aerogel with ultra low dielectric constant
A polyimide (PI) aerogel with excellent combined thermal and dielectric properties was successfully prepared by the polycondensation of 3,3',4,4' biphenyltetracarboxylic dianhydride (BPDA) 5 amino 2 (4 aminophenyl)benzoxazole (APBO) and octa(amino phenyl)silsesquioxane (OAPS) crosslinker, followed by a supercritical carbon dioxide (scCO2) drying treatment. The developed PI aerogel exhibited an ultra low dielectric constant (k) of 1.15 at a frequency of 2.75 GHz, a volume resistivity of 5.45*10 14 *cm, and a dielectric strength of 132 kV/cm. The flexible PI aerogel exhibited an open pore microstructure consisting of three dimensional network with tangled nanofibers morphology with a porosity of 85.6% (volume ratio) an average pore diameter of 19.2 nm, and a Brunauer Emmet Teller (BET) surface area of 428.6 m 2 /g. In addition, the PI aerogel showed excellent thermal stability with a glass transition temperature (Tg) of 358.3 degC, a 5% weight loss temperature over 500 degC, and a residual weight ratio of 66.7% at 750 degC in nitrogen.