Micellization and adsorption characteristics of CHAPS
Micellization and adsorption characteristics of CHAPS
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DOI：
10.1021/la9913708
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发表时间：
2000-05-30
期刊：
影响因子：
3.9
通讯作者：
Norde, W
中科院分区：
文献类型：
--
作者：
Giacomelli, CE;Vermeer, AWP;Norde, W
通过测定吸附量和吸附焓，在22和36 ℃下研究了CHAPS在疏水胶乳颗粒上的吸附。将吸附过程与表面活性剂的胶束化过程进行了比较。因此，临界胶束浓度（cmc）和胶束化热也确定在这两个温度。从这两个量的吉布斯能量和熵的过程中计算。cmc和胶束化热是温度依赖性的; cmc随着温度升高而增加，并且胶束化热从22 ° C的正变为36 ° C的负。在胶束化过程中存在熵-焓补偿，表现出疏水相互作用的特征。最大吸附量与温度无关，而等温线的初始斜率在22 ℃时略陡。虽然吸附过程在两个温度下都是放热的，但吸附焓在36 ℃时更负。由于吸附过程在22 ℃下更有利，因此对整个过程有很大的熵贡献，表明疏水相互作用也主导了CHAPS在胶乳颗粒上的吸附。表面活性剂甾核中羟基的取向是CHAPS聚集和吸附的主要原因。事实上，胶束化和吸附过程的机制是密切相关的：两者都是由CHAPS分子的非极性面之间的疏水相互作用（胶束化）或分子的疏水部分与疏水胶乳颗粒表面之间的疏水相互作用（吸附）驱动的。
The adsorption of CHAPS on hydrophobic latex particles was studied at 22 and 36 degrees C by determining the adsorbed amount and the enthalpy of adsorption. The adsorption process was compared to the micellization of the surfactant. Therefore, the critical micelle concentration (cmc) and the heat of micellization were also determined at both temperatures. From these two quantities the Gibbs energy and the entropy of the process were calculated. The cmc and the heat of micellization are temperature dependent; the cmc increases as the temperature rises, and the heat of micellization goes from positive at 22 degrees C to negative at 36 degrees C. There is an entropy-enthalpy compensation in the micellization process, characteristic of hydrophobic interactions. The maximum adsorbed amount is independent of the temperature, while the initial slope of the isotherms is slightly steeper at 22 degrees C. Although the adsorption process is exothermic at both temperatures, the enthalpy of adsorption is more negative at 36 degrees C. Since the adsorption process is more favorable at 22 degrees C, there is a substantial entropy contribution to the overall process, suggesting that hydrophobic interactions are also dominating the adsorption of CHAPS on latex particles. The orientation of the hydroxyl groups in the steroid nucleus of the surfactant is mainly responsible for the aggregation and adsorption behavior of CHAPS. Indeed, the mechanisms of the micellization and the adsorption processes are strongly related: both are driven by hydrophobic interactions between the apolar faces of the CHAPS molecules (micellization) or between the hydrophobic parts of the molecules and the hydrophobic latex particle surface (adsorption).