Danino D, Talmon Y, Zana R
Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa, 32000, Israel
J Colloid Interface Sci. 1997 Feb 1;186(1):170-9. doi: 10.1006/jcis.1996.4599.
Mixtures of water and of the nonionic surfactant C12E8 (octaoxyethyleneglycol monododecylether) have been investigated by time-resolved fluorescence quenching (TRFQ) and transmission electron microscopy at cryogenic temperature (cryo-TEM) to obtain information on the size and shape of the surfactant aggregates and on the microstructure of the mixtures. The studies were performed at surfactant contents and temperatures where the micelles grew significantly and also where the systems undergo phase transitions from micellar-to-cubic upon increasing surfactant content or decreasing temperature and from cubic-to-hexagonal-to-micellar upon increasing temperature. No rapid change or discontinuity was observed in the variation of the aggregation number with the surfactant content or temperature upon crossing the micellar-to-cubic phase boundary nor at the approach of the hexagonal phase from the cubic phase. The results confirmed that the cubic phase consists of spheroidal micelles forming a three-dimensional array. The aggregation numbers at high surfactant content or temperature can be much larger than that of the minimum spherical micelle for a surfactant with a dodecyl chain, suggesting that the micelles should be anisotropic. However, cryo-TEM showed that in the micellar phase the micelles are always spheroidal. These apparently inconsistent results are explained in terms of a partial mixing of the surfactant dodecyl chains and octaoxyethylene head groups which allows for spheroidal micelles of aggregation number much larger than for a surfactant with a dodecyl chain. The results show extensive exchange of material at 40°C, taking place most likely via temporary merging of micelles in micelle clusters then present in the system.
通过时间分辨荧光猝灭（TRFQ）和低温透射电子显微镜（cryo-TEM）研究了水与非离子表面活性剂C12E8（八氧乙烯基单十二烷基醚）的混合物，以获取有关表面活性剂聚集体的尺寸和形状以及混合物微观结构的信息。研究是在表面活性剂含量和温度条件下进行的，在这些条件下胶束显著生长，并且当表面活性剂含量增加或温度降低时，体系会发生从胶束相到立方相的相变，而当温度升高时，体系会发生从立方相到六方相再到胶束相的相变。在跨越胶束相到立方相的相边界时，以及在从立方相接近六方相时，未观察到聚集数随表面活性剂含量或温度的变化有快速变化或不连续性。结果证实立方相由形成三维阵列的球形胶束组成。在高表面活性剂含量或温度下的聚集数可能比具有十二烷基链的表面活性剂的最小球形胶束的聚集数大得多，这表明胶束应该是各向异性的。然而，cryo-TEM表明在胶束相中胶束总是球形的。这些明显不一致的结果可以用表面活性剂十二烷基链和八氧乙烯头基的部分混合来解释，这种混合允许聚集数比具有十二烷基链的表面活性剂大得多的球形胶束形成。结果表明在40℃时发生了广泛的物质交换，最有可能是通过当时存在于体系中的胶束簇中胶束的临时合并来进行的。
