Li Yajuan, Reeve James, Wang Yilin, Thomas Robert K, Wang Jinben, Yan Haike
Key Laboratory of Colloid and Interface Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
J Phys Chem B. 2005 Aug 25;109(33):16070-4. doi: 10.1021/jp0523874.
The micellization of a novel family of nonionic surfactants poly(oxyethylene) glycol alkyl ethers has been studied by microcalorimetry. One of the surfactants has adamantane, and the other nonionic surfactants have a benzene ring in their hydrophobic chains, which moves from the terminal of the hydrophobic chain toward the headgroup. Moreover, the alkyl chain of the nonionic surfactants is straight or branched. Both the critical micelle concentration (cmc) and the thermodynamic parameters associated with the micelle formation have been obtained. The cmc decreases and the enthalpy of micelle formation (deltaH(mic)) becomes less positive gradually as the length of hydrophobic chain increases, whereas the values of cmc and deltaH(mic) tend to increase for the surfactants with a longer ethylene oxide chain. However, the deltaH(mic) value of the surfactant with seven carbon atoms in a hydrophobic chain is more positive than that of the surfactant with six carbon atoms in a hydrophobic chain. Comparing with the nonionic surfactant with a methylene hydrophobic chain, the surfactants with benzene rings and adamantane groups have larger cmc values and the cmc values increase with the size of the groups. Furthermore, moving the phenyl group from the terminal of the hydrophobic chain to the neighbor of the hydrophilic headgroup leads to the decreased cmc. Both the variation of hydrophobic interaction from the movement of phenyl group and pi-pi interaction among adjacent phenyl groups affect deltaH(mic) values.
通过微量量热法研究了一类新型非离子表面活性剂聚（氧乙烯）二醇烷基醚的胶束化作用。其中一种表面活性剂含有金刚烷，其他非离子表面活性剂在其疏水链中含有苯环，该苯环从疏水链末端向头基移动。此外，非离子表面活性剂的烷基链是直链或支链。已获得临界胶束浓度（cmc）以及与胶束形成相关的热力学参数。随着疏水链长度增加，cmc降低，胶束形成焓（deltaH(mic)）逐渐变得不那么正值，而对于环氧乙烷链较长的表面活性剂，cmc和deltaH(mic)值趋于增加。然而，疏水链中含有七个碳原子的表面活性剂的deltaH(mic)值比疏水链中含有六个碳原子的表面活性剂的deltaH(mic)值更正。与具有亚甲基疏水链的非离子表面活性剂相比，含有苯环和金刚烷基团的表面活性剂具有更大的cmc值，且cmc值随基团大小增加。此外，将苯基从疏水链末端移至亲水头基附近会导致cmc降低。苯基移动引起的疏水相互作用变化以及相邻苯基之间的π-π相互作用都会影响deltaH(mic)值。
