Keywords: nanocomposites, layered double hydroxide, aluminium, zinc, polyethylene oxide, surface treatment, titanium dioxide, nanoparticles, nanotechnology, polymeric coating, polymer crystallinity, glass transition behaviour
In situ preparation of nanocomposites by surface treatment of titanium dioxide particles with a layered double hydroxide
It is difficult to incorporate nanoparticles in a matrix because the huge number of particles and their enormous surface area dictate that one must expend large amounts of energy in dispersing them and one must find ways to maintain their separation because their surface chemistry is often sufficiently different from the matrix that flocculation via phase separation must be overcome. In many technologies, titanium dioxide is a common white pigment. There is commonly a surface treatment on titanium dioxide particles of a mixed aluminium hydroxide which is partially soluble and is thus available to participate in the formation of a layered double hydroxide, LDH. Thus an in situ preparation of a nanocomposite comprising an LDH and a polymer would take advantage of the presence of the pigment and provide potentially useful gains in physical properties. A zinc–aluminium LDH was precipitated on TiO2 particles. X–Ray diffraction confirmed the structure of the LDH and one could detect the change in surface chemistry of the TiO2 particles by examining their zeta potential in an aqueous dispersion. These materials were incorporated into simple polymeric coating films using polyethylene oxide where the LDH treated particles improved the mechanical properties of the polymer and changed the polymer crystallinity and its glass transition behaviour.