Study on the Structure, Shape, and Solution Properties of nonionic Surfactant Micelles

在这项工作中，我们通过静态（SLS）和动态光散射（DLS）测量表征了典型的非离子表面活性剂聚氧乙烯烷基醚的线状胶束（C_iE_j和j分别表示烷基链上的亚甲基和氧乙烯链上的氧乙烯基的数目）。表面活性剂研究样本C_ < 12 > E_5, C_ < 12 > E_6, C_ < 12 > E_7, C_ < 14 > E_6, C_ < 14 > E_8, C_ < 16 > E_7, C_ < 16 > E_8, C_ < 18 > E_7, C_ < 18 > E_8。结果发现，SLS结果的浓度依赖性、旋转半径与胶束摩尔质量之间的关系、流体动力半径与胶束摩尔质量之间的关系都可以用虫状球柱模型的相应理论很好地表示，从而表明上述表面活性剂形成的胶束呈柔性圆柱形。发现胶束长度随浓度的增加和温度的升高而增加，对于较大的i（或较长的疏水性基团），胶束长度的增长幅度更大。随着i和j的取值，胶束表面表面活性剂分子亲水性基团之间的平均间距约为1.2 ~ 1.5 nm，几乎与表面活性剂种类无关。通过温度升高对胶束溶液进行相分离，发现疏水链较长的表面活性剂具有较低的LCST行为。结果表明，C_<12 bb_0 E_6胶束使胶束形状由虫状球圆柱状转变为长条形椭球状，并吸收正十二烷和正十二醇。在这里，通过加入前一种油，胶束被分解成更小的尺寸，而通过加入后一种油，胶束的尺寸变大。

In this work, we have chracterized threadlike micelles of typical nonionic surfactants polyoxyethylene alkyl ether C_iE_j i and j denote the numbers of methylene groups in the alkyl chain and of oxyethylene groups in the oxyethylene chain, respectively) by static (SLS) and dynamic light scattering (DLS) measurements. The surfactant samples examined are C_<12>E_5, C_<12>E_6, C_<12>E_7, C_<14>E_6, C_<14>E_8, C_<16>E_7, C_<16>E_8, C_<18>E_7, C_<18>E_8.The concentration dependence of the SLS results, the relationships between radius of gyration and micellar molar mass, the relationships between hydrodynamic radius and micellar molar mass are found to be well represented by the corresponding theories with wormlike spherocylinder model, thereby indicating that the micelles formed of the above surfactants assume flexible cylindrical shape. It has been found that the micelles grow in length with increasing concentration and with raising temperature, to greater extent for larger i (or for the longer hydrophobic groups). The cross-sectional diameter has varied from 2.4 to 3.0 nm depending on the valuses of i and j, while the average spacings among hydrophilic groups of the surfactant molecules on the micellar surface are ca. 1.2 -1.5 nm, almost independent of the surfactant species. The micellar solutions have been phase-separated with raising temperature, revealing the LCST behavior with lower LCST for the surfactant with longer hydrophobic chain. It hs been shown that the C_<12>E_6 micelles cause transition of the micellar shape from wormlike spherocylindrical shape to prolate ellipsoid with uptake of n-dodecane and n-dodecanol. Here, the micelles have been disintegrated into smallar size by including the former oil, while they have grown in size by inchsding the latter.