Macroporous Morphology of the Titania Films Prepared by a Sol-Gel Dip-Coating Method from the System Containing Poly(ethylene glycol). IV. General Principle of Morphology Formation and Effect of Heat Treatment

The variation of macroscopic morphology of the titania (TiO₂) films has been studied at various dipping conditions for a sol-gel dip-coating system containing poly(ethylene glycol) (PEG). The variation of macroscopic morphology is understood consistently by considering both the volume fraction of solvent phase during the phase separation and the water to alkoxide ratio in the sol film. The gel film shrinks and the average pore diameter increases concurrently with the thermal decomposition of PEG while the morphology depends less on the crystallization of titania gel.