New photosensitive colorless polyimide-silica hybrid optical materials: Synthesis, properties and patterning

We report the synthesis, properties, and patterning of non-fluorinated photosensitive polyimide-silica hybrid optical materials. End-functionalized ionic salt photosensitive poly(1,4-bis(3,4-dicarboxyphenoxy)-2,5-ditertbutylbenzene-dianhydride-co-oxydianiline) (DDBBDA-ODA)/2-methylacrylic acid 2-dimethylamino ethyl ester (MDAE) was prepared first. It was then reacted with tetramethoxysilane (TMOS)-derived silica sol and 3-methacryloxypropyl trimethoxysilane (MSMA) to obtain the ultralow volume shrinkage hybrid optical materials. The experimental results showed the nano-silica domain and the crosslinked structures significantly enhanced the thermal properties, such as the glass transition temperature and coefficient of thermal expansion. The prepared hybrid film not only exhibited high transparency in the visible region but also had tunable refractive index, low birefringence and optical loss by introducing the silica moiety. The SEM image suggested the prepared photosensitive hybrid materials could obtain fine lithographical patterns with an excellent dimensional stability. The combination of excellent optical properties and dimensional stability suggested the potential applications of the prepared hybrid materials for optoelectronic device applications.