Novel low-κ polyimide/mesoporous silica composite films: Preparation, microstructure, and properties

A series of novel low-dielectric constant (low-κ) polyimide (PI) composite films containing the SBA-15 or the SBA-16-type mesoporous silica were successfully prepared via in situ polymerization and following thermal imidization. Their morphologies, dielectric constants, and thermal and dynamic mechanical properties were investigated. It is found that the dielectric constants of the composite films can be reduced from 3.34 of the pure PI to 2.73 and 2.61 by incorporating 3wt% SBA-15 and 7wt% SBA-16, respectively. The reduction of the dielectric constant is attributed to the incorporation of the air voids (κ=1) stored within the mesoporous silica materials, the air volume existing in the gaps on the interfaces between the mesoporous silica and the PI matrix, and the free volume created by introducing large-sized domains. The PI/mesoporous silica composite films prepared in this study also present stable dielectric constants across the wide frequency range and a good phase interconnection. The improvement of the thermal stability and dynamic mechanical properties of the PI film is achieved by incorporation of the mesoporous silica materials. The enhanced interfacial interaction between the surface-treated mesoporous silica and the PI matrix has led to the minimization of the deterioration of the mechanical properties. The incorporation of the mesoporous silica materials is a promising approach to prepare the low-κ PI films.