Laser reflectometry to investigate adsorption–desorption of poly(styrene sulfonate) onto polyamide 6.6

The adsorption of poly(styrene sulfonate) (PSS) on polyamide 6-6 was investigated using fixed angle laser reflectometry. The appropriate polyamide film thickness for an accurate analysis was first determined theoretically. Polyamide films were further prepared at controlled thickness using dip-coating processes and characterized. The adsorption of PSS was measured at pH 3 on dip-coated films as a function of time and polymer concentration. The adsorption rate at very low polymer coverage revealed diffusion limited adsorption. At and above pH 10, the PSS adsorption/desorption was difficult to evaluate. At and above pH 11.5, the hydrolysis of polyamide produced artifacts that prevent any meaningful measurements. This work showed that reflectometry is an interesting analytical tool in the in situ study of the functionalization of organic materials and to investigate the stability of the films produced.