Inclusion of covalent triazine framework into fluorinated polyimides to obtain composites with low dielectric constant

ABSTRACT Polyimides possess good mechanical properties, favorable dielectric properties, and chemical inertness, which enabled them to find applications in microelectronic industries. The dielectric constant of the polyimides varies between 2.5 and 4, which is rather high for such applications. Hence, synthesizing polyimides with still lower dielectric constant has become one of the critical research confronts. As the properties of a terpolyimides (TPI) could be altered as per the requirement, it was synthesized by combining the dianhydrides 3,3′,4,4′‐biphenyldianhydride, 3,3′,4,4′‐oxydiphthalicdianhydride, and 4,4′‐(hexafluoroisopropylidene) with a diamine 4,4′‐(hexafluoroisopropylidene)dianiline or 2,2‐bis[4‐(4‐amino phenoxy)phenyl]hexafluoropropane. As porous covalent triazine framework (CTF‐1) is capable of capturing much air within its pores and interfacial voids, it was combined with the TPI matrix in different loadings to obtain CTF‐1/TPI composite films with low dielectric constant. The composites exhibited high thermal stability, as their thermal decomposition occurred above 520°C. The tensile properties and the dielectric constant of the composites declined with the raise in CTF‐1 loading up to 4%. The decrease in dielectric constant is essentially due to the incorporation of air voids (dielectric constant of air ~1) in the TPI matrix due to the inclusion of porous CTF‐1.