Hybrid titanium dioxide/PS-b-PEO block copolymer nanocomposites based on sol-gel synthesis.

The poly(styrene)-b-poly(ethylene oxide) (SEO) amphiphilic block copolymer, with two different molecular weights, has been used as a structure directing agent for generating nanocomposites of TiO(2)/SEO via the sol-gel process. SEO amphiphilic block copolymers are designed with a hydrophilic PEO-block which can interact with inorganic molecules, as well as a hydrophobic PS-block which builds the matrix. The addition of different amounts of sol-gel provokes strong variations in the self-assembled morphology of TiO(2)/SEO nanocomposites with respect to the neat block copolymer. As confirmed by atomic force microscopy (AFM), TiO(2)/PEO-block micelles get closer, forming well-ordered spherical domains, in which TiO(2) nanoparticles constitute the core surrounded by a corona of PEO-blocks. Moreover, for 20 vol% sol-gel the generated morphology changes to a hexagonally ordered structure for both block copolymers. The cylindrical structure of these nanocomposites has been confirmed by the two-dimensional Fourier transform power spectrum of the corresponding AFM height images. Affinity between titanium dioxide precursor and PEO-block of SEO allows us to generate hybrid inorganic/organic nanocomposites, which retain the optical properties of TiO(2), as evaluated by UV-vis spectroscopy.