Polymerization and surface behavior of alkyl-substituted aniline surfactants at the air-aqueous interface: A kinetic study
The surface behavior of 2-, 3-, and 4-pentadecylaniline (3a, 3b, and 3c, respectively) was studied at the air-aqueous interface of an acidic subphase. Surface dipole moments (μn) were calculated from the surface potentials (ΔV) of 3a-c and were related to the orientation of the anilinium ion at the interface. Further, 3a and 3b were polymerized in a Langmuir film, and analysis of the absorption spectra showed that the resulting polymers were in different oxidative states upon completion of the polymerization. A method that monitors the change in the mean molecular area (A) of the surfactant at a constant applied surface pressure and predicts the concentrations of monomer and polymer and/or oligomer at the interface in order to determine the formation rate (Rp) of poly(alkylaniline) is presented. The Rp values of 3a and 3b are expressed in terms of the concentrations of the monomer and polymer at the interface. It was determined that the Rp of 3a was dependent on the applied surface pressure while 3b showed little dependence on surface pressure. Differences in Rp can be explained by the conformation of the anilinium group and the steric hindrance of the alkyl group at the interface. A characteristic "autoacceleration effect" was observed for both 3a and 3b but was more significant in the case of 3a.
Publication Source (Journal or Book title)
Kloeppner, L., & Duran, R. (1998). Polymerization and surface behavior of alkyl-substituted aniline surfactants at the air-aqueous interface: A kinetic study. Langmuir, 14 (23), 6734-6742. https://doi.org/10.1021/la980330l