Pérez Sofía V, Olea Andres F, Gárate M Pilar
Departamento de Industrias, Universidad Técnica Federico Santa María, Av. Espana 1680, Valparaíso, Chile.
Curr Top Med Chem. 2014;14(6):774-80. doi: 10.2174/1568026614666140118222419.
The formation of reverse micelles by nonionic alcohol ethoxylates surfactants in two "dry" non polar solvents, heptane and dibutoxymethane (DBM), has been studied. These surfactants are formed by a linear hydrocarbon chain consisting of i carbons, and a poly(ethylene oxide) chain with j ethoxylate units (EO) ending with a hydroxyl group, CiEOj. The study is focused on the determination of the critical micelle concentration CMC and the size and morphology of the formed aggregates. The CMC was obtained from the decreasing of interfacial tension with increasing surfactant concentration and by using pyrene sulfonic acid sodium salt as fluorescence probe. The results show that the CMC in heptane is one order of magnitude higher than in DBM and two orders of magnitude higher than those determined in aqueous solution. The self-diffusion coefficients D of C8EO5, C8EO4 and C10EO6 in heptane, were obtained by diffusion ordered spectroscopy (DOSY (1)H-NMR). The experimental values of D were then fitted to four different configurations to determine the most probable morphology of the formed aggregates. In all cases the presence of large and compact aggregates, with aggregation numbers going from a few dozens of monomers to a hundred of them, was shown.
研究了非离子醇乙氧基化物表面活性剂在两种“干燥”非极性溶剂庚烷和二丁氧基甲烷（DBM）中形成反胶束的情况。这些表面活性剂由含有i个碳原子的直链烃链和带有j个乙氧基单元（EO）且末端为羟基的聚环氧乙烷链（CiEOj）组成。该研究聚焦于临界胶束浓度（CMC）的测定以及所形成聚集体的尺寸和形态。通过随着表面活性剂浓度增加界面张力的降低，并使用芘磺酸钠盐作为荧光探针来获得CMC。结果表明，庚烷中的CMC比DBM中的高一个数量级，比在水溶液中测定的高两个数量级。通过扩散排序光谱法（DOSY (1)H-NMR）获得了C8EO5、C8EO4和C10EO6在庚烷中的自扩散系数D。然后将D的实验值拟合到四种不同构型，以确定所形成聚集体最可能的形态。在所有情况下，均显示存在大而紧密的聚集体，聚集数从几十到上百个单体不等。
