Diblock copolymer templated nanohybrid thin films of highly ordered TiO₂ nanoparticle arrays in PMMA matrix

Solvent modification with a mixture of tetrahydrofuran and water in a proportional volume ratio of 50% has been employed to enable poly(methylmethacrylate)-b-polyethylene oxide diblock copolymer to be used as a template for preparing nanohybrid thin films containing highly ordered arrays of titanium dioxide (TiO₂) nanoparticles. With control of the processing parameters involved in the block copolymer templating, nanoarrays consisting of nanocrystalline TiO₂ particles were successfully assembled in the hexagonal-like or cubical-like hierarchical structures, as revealed by TEM studies. The phases and chemical nature of the titania nanoparticles have been confirmed by Raman and XPS spectroscopies. A significant enhancement in nanocrystallinity of the TiO₂ phase in the nanohybrid thin films was achieved by the application of an appropriate hydrothermal treatment in high-pressure water vapor at 150°C. The nanocrystallinity strongly affects the UV absorbance and photoluminescence emission of the nanohybrid thin films.