Line tension at freezing transition of alkane wetting film on aqueous surfactant solutions

The line tension of tetradecane lens on the aqueous solutions of cationic surfactant, tetradecyltrimethylammonium bromide were measured as a function of surfactant concentration at the wetting transition between partial wetting and pseudo-partial wetting and as a function of temperature at the freezing transition of the pseudo-partial wetting film. In both experiments, the reversal of the line tension sign was observed; from positive to negative in the former and from negative to positive in the latter. These observations were analyzed based on the interface displacement model and explained by the change in the free energy of unit area of the wetting film at the air–water interface.

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► The line tension of alkane lens on the cationic surfactant solution was investigated by varying concentration and temperature.
► Wetting transition between partial wetting and pseudo-partial wetting and the freezing transition of the pseudo-partial wetting film was observed.
► The line tension sign was reversed from + to − at wetting transition and from − to + at freezing transition.
► Experimental results were analyzed based on the interface displacement model.