Understanding the Supramolecular Self-Assembly of Zirconium Titanate Mesophases Formed from the Poly(ethylene oxide) Surfactant Brij-58

The evaporation-induced self-assembly of mesoporous zirconium titanium oxide thin films prepared from precursor solutions with the composition ZrxTi1−xCl4:40 EtOH:0.005 Brij 58:h H2O (where x = 0.28, h = 10, and Brij 58 = diblock copolymer C16H33PEO20) by dip coating has been studied as a function of the mole fraction of zirconium (x), the relative humidity (RH), and the drying conditions. Extremely well-ordered mesophases and compositional homogeneity on the atomic scale were consistently obtained when the films were prepared at relative humidities above 60%, under which conditions a cubic phase was identified. The influence of humidity was monitored using a combination of in situ small-angle X-ray diffraction (SAXD) and small-angle X-ray scattering (SAXS). These techniques showed the existence of nanocrystalline phases during the initial drying process for films prepared from precursor solutions with x in the range of 0.20−0.60. The nanocrystalline phases were evidenced as multiple X-ray reflections abo...