Composition and temperature effects on the solution structure of SDS/octanol/brine by SANS, NMR and microscopy.
Composition and temperature effects on the solution structure of SDS/octanol/brine by SANS, NMR and microscopy.
复制标题
通过 SANS、NMR 和显微镜观察组成和温度对 SDS/辛醇/盐水溶液结构的影响。
作者：
Donina L
采用小角中子散射（SANS）、光学显微镜和核磁共振（NMR）研究了十二烷基硫酸钠/正辛醇/盐水三元混合物模型溶液在层状相（L α）、囊泡相（L4）和胶束相（L1）的结构。具体地，我们在固定的辛醇：SDS比率（0.08 - 1.21）下沿着稀释线检查助表面活性剂辛醇（0.2 - 9.48 w/v %）和温度（25 - 65 ° C）的影响。 发现在高于35 ° C时，沿着辛醇：SDS = 1.21的等值线，沿着从L α到海绵相（L3）的转变，表面活性剂和助表面活性剂的重量分数高于0.14时相共存。 稀释后的层状双层膨胀，与d-间距的近似线性增加，伴随着Caillé参数的降低，表明更大的膜刚度。在较低的辛醇：SDS的比例为0.62，扁圆胶束和囊泡的共存观察优先形成的囊泡在低浓度。 稀释的L1相，沿着辛醇：SDS = 0.08，结果在细长的胶束，作为NaCl：SDS的比例增加，而较高的温度有利于形成较短的细长胶束。 我们的研究结果提供了一个详细的平衡结构的地图，发现在L α附近的这个广泛研究的流动响应表面活性剂系统。
We investigate the solution structures of model sodium dodecyl sulfate/octanol/brine ternary mixtures across the lamellar (Lα), vesicle (L4) and micellar (L1) phases employing small angle neutron scattering (SANS), optical microscopy and nuclear magnetic resonance (NMR). Specifically, we examine the effect of co-surfactant octanol (0.2–9.48 w/v%) and temperature (25–65 °C) along dilution lines at fixed octanol : SDS ratios (0.08–1.21). A transition from Lα to sponge phase (L3) above 35 °C is found along the octanol : SDS = 1.21 isopleth, with phase coexistence above ϕ ≈ 0.14 weight fraction of surfactant and co-surfactant. The lamellar bilayers swell upon dilution, with an approximately linear increase of d-spacing, accompanied by a decrease of the Caillé parameter, indicative of greater membrane rigidity. At a lower octanol : SDS ratio of 0.62, coexistence of oblate micelles and vesicles is observed with preferential formation of vesicles at low concentrations. Dilution of the L1 phase, along octanol : SDS = 0.08, results in elongated micelles, as the NaCl : SDS ratio increases, while higher temperatures favour the formation of less elongated micelles. Our results provide a detailed map of the equilibrium structures found in the Lα vicinity of this extensively investigated flow-responsive surfactant system.