Interphase volume calculation of polyimide/TiO₂ nanofibers nanocomposite based on dielectric constant model and its effect on glass transition

This work demonstrates the significant interphase region of polyimide/titanium dioxide nanofiber nanocomposite. Interphase characteristics of nanocomposites were calculated using Interphase Power Model. It revealed that the interphase volume fraction and interphase dielectric constant were proportionately increased with filler loading at least up to 20%. The increasing trend of interphase dielectric constant signifies a loosely bounded polymeric chain onto the filler surfaces giving the interphase volume constant k as 2.05. However, the ratio of interphase volume to that of the filler volume progressively decreased which was attributed to the effect of agglomeration of filler and percolation of overlapping interphase region to yield an average interphase thickness of 81 ± 10 nm. By designing the complex function of interfacial interaction through the surface activity between the filler and matrix, the interphase region can be appropriately monitored in understanding its effects on glass transition and dielectric constant of the nanocomposites.