Highly transparent, strong, and flexible fluorographene/fluorinated polyimide nanocomposite films with low dielectric constant

Optimization of molecular interactions between filler materials and a polymer matrix is one of the key methods to improve the dielectric properties of composite films. In films composed of two-dimensional fluorographene (FG) and fluorinated polyimide (f-PI), the repulsion between the C-F bonds hinders the dispersion of the filler in the matrix. In this work, we describe a low dielectric constant FG/f-PI nanocomposite film obtained by the preparation of f-PI on exfoliated FG grafted with 2,20-bis(trifluoromethyl)-[1,10-biphenyl]-4,40-diamine (t-FG). The strong interfacial interaction between f-PI and t-FG promotes the dispersion of t-FG in the f-PI matrix. The effects of the addition of t-FG on the optical, mechanical, and dielectric properties of the composite film are investigated by incorporating different amounts of t-FG. When the t-FG content reaches 0.75 wt%, we obtain a transparent, strong, and flexible t-FG/f-PI composite film, which exhibits a low dielectric constant (2.09) and a high tensile strength (300.1 MPa). An organic thin-film transistor fabricated using this film as a dielectric layer exhibits good transistor mobility and ON/OFF ratio. t-FG/f-PI dielectric films are therefore suitable for application in transparent flexible displays.