Interfactant action of an amphiphilic polymer upon directing graphene oxide layer formation on sapphire substrates

Quality assured surface pre-treatment may greatly enhance adhesive interactions and, thus, the performance and durability of material joints. This holds true as well for substrates used in coating processes as for adherents introduced into bonding processes. Wettable polymeric wetting agents—shortly called polymeric interfactants—contribute to modifying surfaces and governing the properties of interphases. This is demonstrated for amphiphilic polymers directing the adsorption of graphene oxide (GO) nano-sheets from aqueous dispersion on alumina surfaces. In this contribution, contact angle measurements as well as X-ray photoelectron spectroscopy and scanning force microscopy investigations are applied for the characterization of thin films. GO is adsorbed either from a buffered dispersion on pristine aluminum oxide surfaces or on alumina modified with a few nanometers thin layer of a polymeric interfactant. Laterally extended nanoparticles and GO nano-sheets are preferentially found on interfactant layers whereas on pristine aluminum oxide smaller adsorbates dominate. The driving forces directing the GO attachment are discussed using a phenomenological model based on polymer/substrate interactions governing the sticking probabilities of GO nano-sheets with different sizes.