Carbon nitride/polyimide porous film via an NIPS method with advanced dielectric and hydrophobicity properties

Herein, an ultra-low dielectric porous polyimide (PPI) composite film was fabricated by non-solvent induced phase separation (NIPS). High-performance carbon nitride nanosheets grafted by heptadecafluoro-1,1,2,2-tetradecyl-trimethoxysilane (CNNF) were incorporated into the PPI film to enhance thermomechanical and hydrophobic properties. The effects of non-solvent and filler content on the porous morphology, dielectric properties, hydrophobicity and thermomechanical properties of films were investigated. The porous morphology of the CNNF/PPI film changed from the coexistence of pipe-like and spongy structure via H2O, to a tightly-stacked porous structure via MeOH as non-solvent. The dielectric constants epsilon ' of 0.5 wt%-CNNF/PPI(H2O) and 0.5 wt%-CNNF/PPI(MeOH) were 1.56 and 1.69 at 1 MHz, respectively, which were similar to 50% lower than that of the original PI film (epsilon ' = 3.33). With the introduction of CNNF, the water contact angle (WCA) of CNNF/PPI(H2O) increased from 66 degrees to 107 degrees and that of CNNF/PPI(MeOH) increased from 92 degrees to 120 degrees. Simultaneously, the storage modulus E ' of 2 wt%-CNNF/PPI(MeOH) reached its highest value of similar to 881 MPa, which was similar to 350 MPa higher than that of PPI(MeOH), together with an enhancement in T-g. This method confirmed a promising prospect for the utilization of porous PI substrates in integrated circuits and microelectronic devices.