Highly fluorinated organic–inorganic nanocomposites with improved refractive index and photopatterning properties

Abstract We developed a highly fluorinated photocrosslinkable nanocomposite that can be applied from solutions in fluorous solvents and has a higher refractive index (RI) compared to the conventional amorphous fluoropolymers. Its two main components are an aromatic fluoroalkylated epoxy binder (RF-FDP-E) and fluoroalkyl ether-type phosphonic acid-substituted anatase titania (TiO2-PEPA) nanoparticles. RF-FDP-E had an RI of about 1.48 at 589 nm and the transmittance of its 270 nm thick film was around 92% in the visible light region. Thin films of RF-FDP-E mixed with small amounts of a photoacid generator (PAG) could be photolithographically patterned by using commercially available hydrofluoroether (HFE) solvents, forming structures with a 10 μm size. The TiO2-PEPA nanoparticles with an average diameter of 18 nm could also be transparently dissolved into the HFE solvents; the RI at 589 nm and transmittance in the visible light region of the resulting 280 nm thick films were 1.65 and 88%, respectively. The thin film (510 nm) obtained from a dissolved mixture of RF-FDP-E and TiO2-PEPA (50% in weight) exhibited RI and transmittance of 1.50 and 87%, respectively, and the original photopatterning properties were maintained.