Synthesis and optical properties of photosensitive polyimide/silica hybrid thin films

In this study, the photopatternable fluorinated polyimide/silica hybrid materials were synthesized by 4,4′-hexafluoroisopropylidenediphthalic anhydride (6FDA), oxydianiline (ODA), aminopropyltriethoxysilane (APrTEOS), and 12 nm colloidal silica with a coupling agent. The monodispersed colloidal silica was used to form a silica domain instead of alkoxysilanes in the conventional process. The coupling agents used were 3-methacryloxypropyl trimethoxysilane (MPTMS) or (4-vinylphenethyl)trimethoxysilane (VPTMS). The coupling agent and the silica domain were designed to reduce the volume shrinkage and enhance the thermal properties, respectively. The retention of 2-methyl acrylic acid 2-dimethylamino-ethyl ester (MDAE) in the prepared hybrid films was supported by X-ray photoelectron spectroscopy (XPS) and thickness variation during the curing process. The particle size of silica in the hybrid materials based on SEM analysis was in the range of 10-25 nm. The prepared hybrid materials also exhibited a reduced refractive index after increasing the silica content. The SEM diagram suggested the prepared photosensitive hybrid materials could obtain lithographical patterns with a good resolution. These results indicate that the newly prepared photosensitive polyimide/silica hybrid materials may have potential applications for optical devices.