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

• Applicant: Professor Dr.-Ing. Guido Grundmeier
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Solid State and Surface Chemistry, Material Synthesis ; Synthesis and Properties of Functional Materials
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 320414069

• Final Report Year: 2020

Final Report Abstract

The results of this research project reveal the interface dominated properties of ZnO-nanostructures in combination with poly(acrylic acid) (PAA) as a polymeric phase. Different substrates such as stainless steel, poly(propylene) (PP) and hotdip galvanized steel (HDG) could be analyzed with regard to the impact of surface modification by means of ZnO-nanostructures and PAA. For metal substrates, the controlled electrochemical deposition of ZnO films with different aspect ratios via the adjustment of the electrolyte composition by adding HMTA was successfully performed. Consequently, in the case of platelet-like ZnO films, hexagonal structures enriched in ZnO polar crystalline facets were obtained. The SMFS results for PAA-modified cantilever clearly showed that coordinative binding of carboxylate groups to surface Zn-atoms dominate the composite properties. Moreover, dwell-time dependent adhesion measurements revealed the diffusion of PAA chains into the gaps of the ZnO NR films resulting in higher effective force values. This could not be reached in the case of platelet-like films, where, instead, equilibrium events as plateaus in the force distance curves could be detected for increasing dwell times. The successful synthesis of ZnO TP in a tube oven process could be used for further investigations. Spray coatings of PP foils with a nanocomposite film consisting of ZnO TP/ PAA show an increase in the shear test forces with increasing concentrations of ZnO TP. The analysis of failure of adhesion shows a breakage in the cores of the ZnO TP by cohesive ZnO crystal failure. This strong molecular adhesion behavior measured by SMFS could also be found on HDG samples coated with ZnO NR and ZnO nanocrystalline films prepared by controlling the hydrothermal growth with sodium citrate according to the project proposal. Here, the strong interactions between PAA and zinc atoms in the ZnO surface lead to a nanoetching of ZnO crystals. Therefore, the pre-treatment of ZnO films with PAA-containing solutions would make a highly industrial interesting improvement of the interfacial properties regarding macroscopic adhesion performance. Moreover, the platelet-like/ nanocrystalline ZnO films show a lower enhancement in the adhesion in comparison to the ZnO NR films even after immersion into PAA containing solutions. Finally, the combination of the usage of ZnO nanostructures with PAA lead to highly interesting, low-cost materials, and surface pre-treatment procedure. Especially, the spray coating in the time scale of some seconds open the door for a lot of industrial applications in in-line processes.

Publications

• Electropolymerisation of acrylic acid on carbon fibers for improved epoxy/fiber adhesion, European Conference on Applications of Surface and Interface Analysis (ECASIA'17), 24.09.2017-29.09.2017 in Montpellier, France
  Bauer, Andreas; Meinderink, Dennis; Giner, Ignacio; Steger, Helmut; Weitl, Johann & Grundmeier, Guido
  
• Electrodeposition of poly(acrylic acid) on stainless steel with enhanced adhesion properties, Surf. Interface Anal., 50, 1224-1229, Feb. 2018
  Meinderink, D.; Orive, A. G. & Grundmeier, G.
  
• Electropolymerization of acrylic acid on stainless steel for improved adhesion properties, 12th European Adhesion Conference and 4th Luso- Brazilian Conference on Adhesion and Adhesives (EURADH 2018 and CLBA 2018), 5.09.2018-07.09.2018 in Lisbon, Portugal
  A. González-Orive, D. Meinderink, F. Sahin, H.C. Schmidt, W. Homberg, G. Grundmeier
  
• Molecular adhesion studies on ZnO nanorod coated stainless steel, 12th European Adhesion Conference and 4th Luso-Brazilian Conference on Adhesion and Adhesives (EURADH 2018 and CLBA 2018), 5.09.2018-07.09.2018 in Lisbon, Portugal
  D. Meinderink, A. G. Orive and G. Grundmeier
  
• Application of AFM-based single-molecule force spectroscopy for the analysis of macromolecular adsorption on nanostructured ZnO films, 3th International Conference on Applied Surface Science (ICASS'19), 17.06.2019-20.06.2019 in Pisa, Italy
  D. Meinderink, A. G. Orive, S. Ewertowski, I. Giner, G. Grundmeier
  
• Dependance of Poly(acrylic acid) Interfacial Adhesion on the Nanostructure of Electrodeposited ZnO Films, ACS Appl. Nano Mater., 2, 831-843, Jan. 2019
  Meinderink, Dennis; Orive, Alejandro Gonzalez; Ewertowski, Simon; Giner, Ignacio & Grundmeier, Guido
  
• Electrografting of Acrylic Acid on Steel for Enhanced Adhesion Properties, 70th Annual Meeting of the International Society of Electrochemistry (ISE), 04.08.2019-09.08.2019 in Durban, South Africa
  A.G. Orive, D. Meinderink, F. Sahin, J. C. Calderón-Gómez and G. Grundmeier
  
• Spray coating of poly(acrylic acid)/ZnO tetrapod adhesion promoting nanocomposite films for polymer laminates, Surf. & Coat. Technol., 375, 112-122, June 2019
  Meinderink, Dennis; Nolkemper, Karlo J.R.; Bürger, Julius; Orive, Alejandro G.; Lindner, Jörg K.N. & Grundmeier, Guido