ABSTRACT

Effect of caffeine on the micellization of anionic surfactant (SDS), cationic surfactant (HTAB) and non-ionic surfactant (Tx-100) was investigated using the conductometric and tensiometric techniques. The thermodynamic parameters such as change in Gibbs-free energy, $\mathrm{\Delta }{G}_m^0$, change in enthalpy of micellization, $\mathrm{\Delta }{H}_m^0$, change in entropy of micellization, $\mathrm{\Delta }{S}_m^0$, change in Gibbs-free energy of transfer, $\mathrm{\Delta }{G}_{m,trans}^0$, surface excess concentration, ${\mathrm{\Gamma }}_{max}$, minimum area per surfactant molecule, $A_{min.}$, surface pressure, ${\mathrm{\Pi }}_{cmc}$, change in Gibbs-free energy of adsorption, $\mathrm{\Delta }{G}_{ads}^0$ and other related parameters were calculated to gain insights into the interactions of caffeine with different surfactants at different temperatures. The CMC in mole fraction units, ${\chi }_{CMC}$, values of SDS in caffeine are low, while that of HTAB are large in comparison with the values reported in water. The negative values of $\mathrm{\Delta }{H}_m^0$ and $\mathrm{\Delta }{G}_m^0$ and the positive values of $\mathrm{\Delta }{S}_m^0$ are indicative of SDS-caffeine and HTAB-caffeine interactions.

摘要

使用电导和张力测量技术研究了咖啡因对阴离子表面活性剂 (SDS)、阳离子表面活性剂 (HTAB) 和非离子表面活性剂 (Tx-100) 胶束化的影响。热力学参数，例如吉布斯自由能的变化，$\mathrm{\Delta }{G}_{米}^0$, 胶束化焓的变化,$\mathrm{\Delta }{H}_{米}^0$，胶束化熵的变化，$\mathrm{\Delta }{\mathrm{小号}}_{米}^0$，转移吉布斯自由能的变化，$\mathrm{\Delta }{G}_{米,吨r\mathrm{一个}ns}^0$, 表面过量浓度,${\mathrm{\Gamma }}_{最大限度}$，每个表面活性剂分子的最小面积，${\mathrm{一个}}_{分钟.}$, 表面压力,${\mathrm{\Pi }}_{C米C}$，吸附的吉布斯自由能的变化，$\mathrm{\Delta }{G}_{\mathrm{一个}ds}^0$计算了其他相关参数，以深入了解咖啡因与不同表面活性剂在不同温度下的相互作用。摩尔分数单位的 CMC，${\chi }_{C米C}$，咖啡因中的 S​​DS 值较低，而与水中报告的值相比，HTAB 的值较大。的负值$\mathrm{\Delta }{H}_{米}^0$和$\mathrm{\Delta }{G}_{米}^0$和正值$\mathrm{\Delta }{\mathrm{小号}}_{米}^0$表示 SDS-咖啡因和 HTAB-咖啡因的相互作用。