| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2002: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
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.
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