Polymerization of 2-pentadecylaniline monolayers at fluid surfaces: kinetics, thermodynamics, and mechanism

Monolayers of 2-pentadecylaniline were polymerized at the air/aqueous acid interface using ammonium persulfate as the oxidizing agent. Isotherms of 2-pentadecylaniline were measured on a 0.1 M sulfuric acid subphase at different temperatures. The mean molecular area at the surface pressure onset was found to increase with temperature. The effect of varying the applied surface pressure and temperature on the polymerization rate of 2-pentadecylaniline at the interface was investigated. Activation energy and other thermodynamic parameters such as enthalpy, entropy, and Gibbs free energy of activation were calculated. The activation energy increased with increasing applied surface pressure. This result was interpreted in terms of intermolecular distances. The polymerization rate at the interface also increased with increasing applied surface pressure at a given temperature. Such experiments allowed the measurement of the activation area at a given temperature. The results cited above are used in interpreting the polymerization mechanism.