Effect of NaCl, n-Butanol, and Temperature on the Micellization of Ammonium Cationic Surfactants (DTAB, TTAB, and CTAB) in Aniline Solution

아닐린 수용액에서 암모늄형 양이온성계면활성제 (DTAB, TTAB, 및 CTAB)의 미셀화에 미치는 염, n-부탄올 및 온도의 효과

Abstract

The criticical micelle concentration (CMC) was measured by using the UV-Vis method for the micellization of the ammonium type cationic surfactants (DTAB, TTAB, and CTAB) in the aqueous aniline solution. The enthalpy change (${\Delta}H^0$) and entropy change (${\Delta}S^0$) were calculated from the dependence of Gibbs free energy change (${\Delta}G^0$) on the temperature for micellization of the cationic surfactants between 290K and 314K. The effects of n-butanol and sodium chloride on the micellization of cationic surfactants were measured and compared with the other thermodynamic functions. All the free energy changes (${\Delta}G^0$) of the micellization were negative, all the enthalpy change (${\Delta}H^0$) were negative, and all the entropy change (${\Delta}S^0$) were positive values, respectively. The micelle formation of cationic surfactant in aniline solution is a spontaneous exothermic reaction, and the iso-structural temperature calculated from the thermodynamic values show that enthalpy and entropy contribution to the micellization are almost the same for the micellization of cationic surfactants

아닐린 수용액에서의 암모늄형 양이온성 계성면활성제 (DTAB, TTAB 및 CTAB)의 미셀화에 대한 임계미셀농도(CMC)값을 UV-Vis법으로 측정하였다. 290K ~ 314K 사이에서 측정된 양이온성 계면활성제의 CMC값의 변화로부터 미셀화에 대한 Gibbs 자유에너지(${\Delta}G^0$)값을 구하고, 이 값으로부터 엔탈피(${\Delta}H^0$)와 엔트로피(${\Delta}S^0$)를 계산하고 분석하였다. 또한 n-부탄올 및 염화나트륨의 농도 변화가 미셀화에 미치는 영향을 열역학적 함수를 이용하여 비교 분석하였다. 실험한 온도 구간 및 첨가제의 농도 범위 내에서 측정된 모든 ${\Delta}G^0$ 값은 음의 값을 나타냈었으며, 엔탈피(${\Delta}H^0$) 변화값은 모두 음의 값을 그리고 엔트로피(${\Delta}S^0$) 변화값은 모두 양의 값을 나타내었다. 아닐린 수용액에서 양이온성 계면활성제의 미셀화는 자발적 발열반응이며, 열역학적 값들로부터 계산된 등구조온도에 의하면 이들 계면활성제의 미셀화는 엔탈피(${\Delta}H^0$)와 엔트로피(${\Delta}S^0$)가 거의 동일하게 기여하고 있음을 알 수 있었다.

Fig. 1. Plots of the absorbance values versus the concentration of surfactants in the 0.2mM aqueous solution of aniline at 302K.

Fig. 2. Plots of ΔG⁰ values against the carbon numbers at the alkyl groups of surfactants for the micellization of cationic surfactants(DTAB, TTAB and CTAB) at 302K.

Fig. 3. Plots of ΔG⁰ values against the concentration of n-butanol for micellization of cationic surfactants (DTAB, TTAB, and CTAB) at 302K.

Fig. 4. Plots of ΔG⁰ values against the concentration of NaCl for the micellization of cationic surfactants (DTAB, TTAB, and CTAB) at 302K.

Fig. 5. Plots of ΔG⁰ values against temperature for the micellization of cationic surfactants (DTAB, TTAB, and CTAB) in pure water.

Fig. 6. Plots of ΔH⁰ values against temperature for the micellization of cationic surfactants (DTAB, TTAB, and CTAB) in pure water.

Fig 7. Plots of ΔS⁰ values against temperature for the micellization of cationic surfactants (DTAB, TTAB, and CTAB) in pure water.

Fig. 8. Plots of the ΔH⁰ values against the ΔS⁰ values for the micellization of cationic surfactants (DTAB, TTAB, and CTAB) in pure water.

Table 1. The values of the critical micelle concentration(CMC) and free energy change (ΔG⁰) for the micellization of cationic surfactants in aqueous solution of aniline containing n-butanol and NaCl at 302K

Table 2. Parameters of the equation (2) for the micellization of cationic surfactants (DTAB, TTAB, and CTAB) in aqueous solution of aniline at 302K

Table 3. Least square parmeters and root mean square deviation (RMSD) of equation (3) and equation (4) relating the ΔG⁰ values with the concentration of n-butanol and NaCl on the micellization of cationic surfactants (DTAB, TTAB, and CTAB) in aqueous solution of aniline at 302K

Table 4. The values of critical micelle concentration (CMC/mM) and thermodynamic functions (ΔG⁰, ΔH⁰, and ΔS°) for the micellization of cationic surfactant (CTAB, TTAB, and DTAB) in aqueous solutions of aniline

Table 5. Least square parameters and root square deviations (RMSD) of equation (5) relating lnXcmc values with the temperature for the micellization of cationic surfactant in 0.2mM solutions of aniline