Adsorption of Dodecyltrimethylammonium Chloride from the Micellar Solution at Water/Air Interface

Abstract

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.

Thermodynamic Study on Vesicle Formation and Adsorption of Decyltrimethylammonium Decyl Sulfate

“…13a and 13b. In DTAC (23), decyltrimethylammonium chloride (DeTAC) or sodium dodecyl sulfate (SDS) systems, s(1) takes much greater values; they are positive in the same temperature range for the former two systems and it is negative but much greater than in the present system for the latter system. Since the monomer state of the surfactant ions in the present system should not be too different from that in these micelle-forming surfactant systems, the adsorbed film formed with DeTA + and DeS − ions is much more ordered and firmly packed compared to that in the micellar systems.…”

“…The higher the temperature, the lower theˆ H values: the hydrocarbon chains of the surfactant ions in the adsorbed film are suggested to be more randomly oriented because of the thermal motion. However, the decrement ofˆ H with temperature at a given molality is much smaller than the other ionic surfactant systems (23,24); for example, in the dodecyltrimethylammonium chloride (DTAC) system atm = 40 mmol kg −1 where the surface is already saturated, theˆ H value decreases from ca. the surface tension measurement of the SDeS-DeTAB mixed surfactant system at the equimolar mixing ratio has proved that the presence of the same amount of NaBr as DeTADeS reduces the saturated value ofˆ H from about 6.00 to 5.60 µmol m −2 at 298.15 K as shown by curve no.…”

Thermodynamics of adsorption of ionic surfactants at water/alkane interfaces

“…In order to simplify the situation at the interface we concentrate here on ionic surfactants the solubility of which in alkanes is extremely low and therefore negligible. One of the very systematically studied homologous series of ionic surfactants is the cationic alkyltrimethylammonium bromide C n TAB, which was intensively investigated at different interfaces in various ways, for example the adsorption dynamics, [24][25][26][27][28] the adsorption isotherms at water/air 16,[29][30][31] or water/alkane interfaces 17,32,33 by tensiometry but also by neutron reection. [34][35][36][37]39 The number of data on alkane co-adsorption at the interface between an aqueous surfactant solution and alkane vapor is rather small, however, there are some rst studies in which also the cationic surfactants C n TAB are investigated (see ref.…”

Thermodynamic Study on the Surface Formation of the Mixture of Water and Ethanol

“…Its purity was more than 99.9% by 16), where alcohols are only slightly soluble in water, it gas chromatography. Water was distilled three times, the was found that the alcohol films exhibit a phase transition last two stages being from alkaline permanganate solution from the condensed to the expanded states by increasing to decompose trace amounts of surface active impurities.…”