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

为了了解纳米粘土/聚电解质薄膜在金属衬底上的成形性，采用逐层聚电解质层生长和剥离纳米粘土吸附相结合的方法在NiTi单晶衬底上沉积了具有特定化学组成的纳米复合薄膜。选择NiTi是因为它的伪弹性性质，以及在这种形状记忆合金的生物医学应用中需要抑制金属释放。选择LBL聚电解质薄膜是因为它具有明确的静电分子间作用力，通过热固化可能将静电相互作用转化为共价键，从而具有特殊的粘弹性性能。通过双官能团有机膦酸的自组装，实现了氧化物覆盖的镍钛合金与复合薄膜之间的界面剪裁。薄膜的结构和化学成分将通过光谱和显微技术进行分析。每个科学小组将进行特殊的补充原位测量，如原位电子显微镜和原位电化学阻抗谱，以研究成型行为和缺陷在成型过程中和之后的形成。因此，薄膜的成形性和自成对性能可以直接与薄膜内部的界面力(聚电解质之间以及聚电解质与纳米粘土之间的界面力)、膜与衬底之间的界面力以及薄膜的形貌相关。此外，还将研究界面作用力的变化和掺水后粘弹性性质对成形性的影响。

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.