Formation of micelles of hexadecyltrimethylammonium bromide in water-N,N-dimethylformamide solutions.
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概要
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The critical micellar concentration of aqueous solutions of hexadecyltrimethylammonium bromide (HTAB) containing various amounts of <I>N</I>,<I>N</I>-dimethylformamide (DMF) has been determined at 25 and 40 °C by means of surface tensiometric measurements. The standard free energy (Δ<I>G</I><SUB>m</SUB><SUP>°</SUP>), enthalpy (Δ<I>H</I><SUB>m</SUB><SUP>°</SUP>) and entropy (Δ<I>S</I><SUB>m</SUB><SUP>°</SUP>) of micellization were also determined. The experimental results indicate that: (1) micelle formation is somewhat hindered by a raise in temperature, and (2) DMF has an inhibitory effect on the formation of micelles of HTAB. This effect is relatively small at low DMF concentrations, but it increases drastically as the mole fraction of DMF approaches 0.33. The changes in the Δ<I>G</I><SUB>m</SUB><SUP>°</SUP>, Δ<I>H</I><SUB>m</SUB><SUP>°</SUP>, and Δ<I>S</I><SUB>m</SUB><SUP>°</SUP> values indicate that the formation of HTAB micelles in the water-DMF mixtures is an entropy directed process at lower concentrations of DMF and the inhibitory effect of DMF on micelle formation is attributed to an increase in the orderliness of this system with increasing DMF concentration.
- 公益社団法人 日本化学会の論文