Swelling of Vesicle Precipitates from Alkyldimethylaminoxide and a Perfluoroalcohol by Refractive‐Index Matching with Glycerol
Swelling of Vesicle Precipitates from Alkyldimethylaminoxide and a Perfluoroalcohol by Refractive‐Index Matching with Glycerol
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DOI：
10.1002/9783527632633.ch5
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发表时间：
2010-11
期刊：
影响因子：
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通讯作者：
Yun Yan;Yuwen Shen;Ying Zhao;H. Hoffmann
中科院分区：
文献类型：
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作者：
Yun Yan;Yuwen Shen;Ying Zhao;H. Hoffmann
甘油对表面活性剂体系的影响越来越受到关注，因为在许多实际配方中不可避免地将它们结合使用[1，2]。例如，用于药物递送的药物制剂使用共溶剂如甘油以改善活性化合物的溶解度或帮助感官知觉。有足够的实验证据表明，表面活性剂在甘油中的自聚集与在水中一样[3-6]，但Krafft点趋于增加，而聚集体的稳定性趋于降低[7-9]，这归因于表面活性剂头部基团的水合作用和疏溶剂效应的变化。已知甘油的加入增加了表面活性剂的CMC并降低了胶束聚集数[10-12]。最近的研究表明，随着甘油浓度的增加，表面活性剂头基的平均面积增加，这伴随着临界堆积参数的降低，因此胶束更小[13]。然而，在水/C12 EO 8体系中，发现胶束聚集体倾向于随着甘油含量的增加而增长，这归因于环氧乙烷链的脱水[14]。甘油带来的上述变化主要集中在微观检查，而宏观相发生的变化很少报道。实际上，在表面活性剂的水性体系中增加甘油的含量时，经常观察到相当大的相和宏观变化[15-18]，表明在自缔合结构水平上发生了相互作用。因此，对该相的物理起源以及甘油引起的其它宏观变化的探讨是十分必要的。最近，我们发现甘油对表面活性剂L α相的影响可能与水-甘油混合溶剂的折射率和表面活性剂双层的折射率的匹配有关[16]。在实验中，我们观察到嵌段共聚物EO 15 [Si（CH 3）2] 3EO 15 L α-相的溶胀，以及在用甘油逐渐替换溶剂水后泡状悬浮液的浊度降低[16]。当甘油浓度为60%时，由于甘油的存在，L1/L α两相体系转变为单一的L α相，
Th effect of glycerol on surfactant systems is gaining increasing attention owing to the inevitable combined use of them in many practical formulations [1, 2]. For example, pharmaceutical formulation for drug delivery uses cosolvents such as glycerol in order to improve the solubility of the active compounds or to aid the sensory perception. There is enough experimental evidence that the surfactant self-aggregation in glycerol occurs as that in water [3–6], but the Krafft point tends to increase, whereas the stability of aggregates tends to decrease [7–9], which was attributed to changes in the hydration of surfactant headgroups and in the solvophobic effect. It has been known that addition of glycerol increases the CMC of surfactants and decreases the micellar aggregation number [10–12]. Recent studies indicate that with increasing glycerol concentration, the average area of the surfactant headgroups is increased, which is accompanied by the decrease of critical packing parameter and therefore of smaller micelles [13]. It was found, however, in the water/C12EO8 system, that micellar aggregates tend to grow with increasing glycerol content, which is attributed to the dehydration of the ethylene oxide chain [14].The aforementioned changes brought about by glycerol mainly focused on the microscopic inspection, whereas what occurs to the macroscopic phases is rarely reported. Actually, upon increasing the content of glycerol in the aqueous systems of surfactants, considerable phase and macroscopic changes are often observed [15–18], indicating that interaction on the level of the self-associated structures has occurred. Therefore, it is very necessary to probe the physical origins of the phase and other macroscopic changes introduced by glycerol. Recently, we found that the influence of glycerol on surfactant L α-phases can be related to the matching of the refractive index of water–glycerol mixed solvent and that of surfactant bilayers [16]. Experimentally, we observed swelling of block copolymer EO 15 [Si (CH 3) 2] 3EO 15 L α-phases and lowering of turbidity for vesicular suspensions upon replacing solvent water gradually with glycerol [16]. At 60% glycerol, the L 1/L α two-phase system is transformed into single L α-phase owing to