Combined in-situ attenuated total reflection-Fourier transform infrared spectroscopy and single molecule force studies of poly(acrylic acid) at electrolyte/oxide interfaces at acidic pH

Fundamental adsorption mechanisms of poly(acrylic acid) (PAA) electrolyte/oxide interfaces were analyzed by the combination of in-situ attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and single molecule force spectroscopy (SMFS). The approach aims at a fundamental understanding of initial states of polymer fouling in chemical microreactors. While the presented FTIR-data provide information on adsorption and desorption kinetics, SMFS studies reveal the corresponding interfacial and intermolecular forces. Silicon oxide and oxide covered FeCr alloy films with small concentrations of Ni were chosen as reference systems for relevant technical reactor components. Adsorption and desorption studies were performed in aqueous electrolytes at acidic pH to simulate the polymerisation process. Ex-situ ellipsometry and atomic force microscopy (AFM) studies of the adsorbed polymer layers as well as X-ray photoelectron spectroscopy (XPS) of the oxide surfaces complemented the analytical approach. The comparison of the in-situ ATR spectroscopic results and the SMFS data revealed higher molecular adhesion forces on FeCr-oxide covered FeCr alloy films in comparison to the SiOx terminated surfaces. The different interactions could be assigned to the specific coordination bonds formed between the carboxylic acid group and surface metal ions in the case of FeCr alloy films. AFM images showed related changes in interfacial film formation.