Macroporous morphology of the titania films prepared by a sol-gel dip-coating method from the system containing poly(ethylene glycol): Effects of molecular weight and dipping temperature

Macroporous morphology has been examined for the titania (TiO2) films prepared by a sol-gel dip-coating method from the system containing poly(ethylene glycol) (PEG) under the variations of molecular weight of PEG and dipping temperature. The macroporous morphology is observed only within the limited range of molecular weight because the compatibility between PEG and the solvent mixture is quite sensitive to the molecular weight. The macroscopic domain formation is enhanced at higher withdrawal speed when the dipping temperature is raised, suggesting that the fluidity reduction and the phase separation are more accelerated than the polycondensation due to the enhanced solvent evaporation.