Investigation of the formability of thin nanoclay containing polyelectrolyte films on NiTi-substrates in humid environments

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For the understanding of the formability of thin nanoclay/polyelectrolyte films on metal substrates, layer-by-layer growth of polyelectrolyte layers in combination with the adsorption of exfoliated nanoclay is performed to deposit nanocomposite films of defined chemistry onto NiTi single crystal substrates. NiTi is chosen due to its pseudoelastic properties and the need to inhibit metal release in case of a biomedical application of this shape memory alloy. LBL polyelectrolyte films are chosen because of the defined electrostatic intermolecular forces and the possible conversion of electrostatic interactions to covalent bonds by thermal curing and the thereby special viscoelastic properties. The interface between the oxide covered NiTi-alloy and the thin composite film will be tailored by the self-assembly of bi-functional organophosphonic acids. The structure and chemical composition of the thin films will be analysed by spectroscopic and microscopic techniques. Each scientific group will perform special complementary in-situ measurements such as in-situ electron microscopy and in-situ electrochemical impedance spectroscopy to study the forming behaviour and the defect formation during and directly after the forming process. Thereby, the formability and selfrepair properties of the thin nanocomposite films can be directly correlated with the interfacial forces within the film (between the polyelectrolytes and between polyelectrolytes and the nanoclay), the interfacial forces between the film and the substrate and the morphology of the thin film. Moreover, the influence of the change in interfacial forces and the viscoelastic properties by incorporated water on the formability will be studied.