Adsorption of poly- DL-alanine at the mercury-solution interface

Abstract

The adsorption of poly- DL-alanine (mean molecular weight 3900) at the mercury-solution interface was studied by means of differential capacity and surface tension measurements. The poly- DL-alanine adsorbed in the potential region between 0.0 and −1.6V( sce). At the potentials of −0.15 and −1.1 V the maximum surface concentration Γ m , and the surface area occupied by one molecule, S, were derived from the diffusion-controlled adsorption behavior with the assumption of the diffusion coefficient. The values of S at −1.1V in 0.1 N sulfuric acid, 0.1N sodium sulfate and 0.1N sodium hydroxide were 348, 282 and 274Å 2/molecule, respectively, and the values at −0.5V became somewhat larger than the above values. The above S values derived from the differential capacity measurement were supported from those derived from the surface tension measurement by means of the Lippmann adsorption equation. The adsorbed conformation at the mercury-solution interface was discussed from those S values.