Comparative Molecular Adhesion Studies of Polyacrylic Acids on ZnO Single Crystal Surfaces and ZnO Nanocrystalline Films

该提案涉及大分子在氧化锌单晶表面和技术相关的纳米晶氧化锌层上的相对粘附性的主题。该项目的基本目标是通过单分子力谱分析水溶液电解质中聚丙烯酸和氧化锌表面之间的界面力和化学。除了范德华力之外，这种界面力包括静电相互作用、氢键和配位键。它们的强度受晶体表面的取向、其终止、吸附物层的性质以及丙烯酸和晶体表面的双电层的影响。这些界面相互作用的分析，应允许与羧酸和氧化锌或氧化锌涂层基板的聚合物之间的微观和宏观的粘附过程的理解。这些粘附过程对于ZnO基复合材料和聚合物涂覆的锌合金在环境和腐蚀条件下的功能性和稳定性非常重要。为了获得这样的界面过程的基本理解，极性和非极性ZnO单晶将进行研究：它们允许的表面终止的详细分析，并在同一时间是稳定的电解质中的界面稳定性相关的环境条件下。ZnO衬底的表面化学将通过非原位电子衍射（LEED）和X射线光电子能谱（XPS）表征;表面形貌和表面电荷将通过扫描原子力显微镜（AFM）原位分析。聚丙烯酸在电解质/氧化物界面的相互作用将通过单分子力谱法使用PEG-连接剂作为表面化学和电解质组合物的函数进行研究。此外，特定的吸附阴离子的吸附/脱附行为的大分子作为不同的晶体取向的函数的影响将进行研究，以了解在腐蚀性环境中的含丙烯酸的聚合物对氧化锌的粘附。类似的研究上进行的纳米晶体ZnO-纳米线层应另外允许的大分子的纯化学吸附与固定化的大分子在ZnO棒之间的有限的间隙中的比较。从这些研究中，我们的目标是获得基本的理解和预测的聚合物/氧化物界面在水性电解质中的界面结合过程。

The proposal addresses the topic of the comparative adhesion of macromolecules onto zinc oxide monocrystalline surfaces and onto technologically relevant nanocrystalline zinc oxide layers. The fundamental aim of this project is the analysis of the interfacial forces and chemistry between polyacrylic acids and zinc oxide surfaces in aqueous electrolytes by means of single molecule force spectroscopy. Beside van-der-Waals forces, such interfacial forces comprise electrostatic interactions, hydrogen bonds and coordinative bonds. Their strength is influenced by the orientation of the crystal surface, its termination, the nature of the adsorbate layer and the electric double layers of the acrylic acid and the crystal surface. The analysis of these interfacial interactions should allow for the understanding of microscopic and macroscopic adhesion processes between polymers with carboxylic acids and zinc oxide or zinc oxide-coated substrates. These adhesion processes are of great importance for the functionality and stability of ZnO-based composite materials and polymer-coated zinc alloys under ambient and corrosive conditions. To gain a fundamental understanding of such interface processes, polar and nonpolar ZnO single crystals will be studied: they allow for a detailed analysis of the surface termination and at the same time are stable under the ambient conditions relevant for interface stability in electrolytes. The surface chemistry of ZnO substrates will be characterised by ex-situ electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS); surface topography and surface charge will be analysed in-situ by means of scanning Atomic Force Microscopy (AFM). The interaction of the polyacrylic acid at the electrolyte/oxide interface will be investigated by means of single molecule force spectroscopy using PEG-linkers as a function of the surface chemistry and the electrolyte composition. Moreover, the influence of specific adsorbed anions on the adsorption/desorption behaviour of the macromolecules as a function of different crystallographic orientations will be studied in order to understand the adhesion of acrylic acid-containing polymers to zinc oxide in corrosive environments. Similar studies performed on nanocrystalline ZnO-nanowire layers should additionally allow for a comparison of the pure chemisorption of the macromolecule with the immobilisation of the macromolecule in the confined gaps between the ZnO rod. From these studies we aim at gaining fundamental understanding and prediction of interfacial binding processes at polymer/oxide interfaces in aqueous electrolytes.