Electrochemical impedance spectroscopy study of waterborne coatings film formation

• EIS was used to study film formation of three waterborne latex coatings.
• Impedance of the coatings increased during film formation.
• Warburg impedance was used to quantify particle deformation and coalescence.
• AFM imaging showing particle deformation and coalescence confirmed EIS results.
• EIS was shown to be suitable for studying latex film formation.

In order to establish electrochemical impedance spectroscopy (EIS) as a viable quantitative method for characterization of latex film formation, three waterborne acrylate and styrene–acrylate polymer dispersions were periodically analyzed during a course of 2 weeks. Impedance spectra were fitted on the base of equivalent circuit consisting of a capacitor in parallel with a Warburg element representing film capacitance and the extent of ion diffusion through the film. Calculated EIS parameter values showed a decrease in Warburg diffusion over time, which is a result of particle coalescence and in agreement with the established theory of latex film formation. Atomic force microscopy (AFM) of the samples showed a smoothing of the surface and blurring of interparticle boundaries which confirmed that EIS can be used to study film formation of latex.