Formation and photopatterning of nanoporous titania thin films

Photopatternable nanoporous titania thin films were generated from mixtures of an organic diblock copolymer, poly(styrene-$b$-ethylene oxide) $(PS-b-PEO)$⁠, and an oligomeric titanate (OT) prepared from a chelated titanium isopropoxide. The $PS-b-PEO$ templates well-defined microdomains in thin films of the mixtures, which upon thermal treatment at $450°C$⁠, become nanopores in titania. Average pore size and porosity are controlled by the molecular weight and loading level of the $PS-b-PEO$⁠, respectively. Patterns of nanoporous titania were created by selectively exposing UV light on the mixture films. The UV irradiation destroys the chelating bond and induces the cross-linking reaction of the OT. Subsequent wet development followed by thermal treatment gives patterned nanoporous films of anatase phase titania.