The surface tension of the aqueous solution of dodecyltrimethylammonium chloride (DTAC) was measured as a function of temperature under atmospheric pressure at concentrations below and above the critical micelle concentration. The thermodynamic quantity changes associated with the adsorption of DTAC from its monomeric and micellar states were evaluated and proved to satisfy the thermodynamic relation derived on the assumption that the micelle formation can be treated as the appearance of a macroscopic bulk phase in the solution. Further their values were compared with those of the aqueous solution of dodecylammonium chloride and the influence of the chemical structure of the head group on the adsorption and micelle formation were discussed from the thermodynamic viewpoint.
The surface tension of the aqueous solution of dodecylmethylammonium chloride (DMAC) and dodecyldimethylammonium chloride (DDAC) was measured as a function of temperature under atmospheric pressure at concentrations below and above the critical micelle concentration (cmc). The entropy and energy of adsorption from the monomeric state in the aqueous solution and the micellar state were evaluated by applying the thermodynamic equations of adsorption to the surface tension values. The thermodynamic quantities were compared with those of the aqueous solutions of dodecylammonium chloride (DAC) and dodecyltrimethylam-monium chloride (DTAC). It was found that the successive N-methylation of DAC has a considerable effect on the adsorbed film with changes in its surface density, entropy, and energy brought about by changes in the geometry and the hydrophilicity of the polar head group.
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