Ultrathin anatase TiO2 films with stable vesicle morphology templated by PMMA-b-PEO

Titania-block-copolymer composite films have been developed with a nanovesicle structure stable enough to survive calcination. An asymmetric diblock copolymer of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) was used as a templating agent, which coupled a good/poor solvent-pair-induced phase separation process with sol-gel chemistry. Various morphologies, including nanovesicles, were obtained and a ternary morphology phase diagram was mapped by variation of the relative weight ratios among 1,4-dioxane, HCl, and titanium tetraisopropoxide (TTIP). AFM and SEM imaging techniques, X-ray reflectivity, and GISAXS characterizations have been combined to study the detailed structure in the film, and the results from different characterization techniques are in good agreement with each other. In addition, it has also been shown that the recipe using a good/bad solvent pair is generally applicable to amphiphilic block copolymers.