Variation of Characteristics of Pentaoxyethylene Decyl C₁₀E₅ and Hexaoxyethylene Tetradecyl C₁₄E₆ Ether Micelles with Uptake of n-Octanol

Abstract

Wormlike micelles of the surfactant pentaoxyethylene decyl C10E5 and hexaoxyethylene tetradecyl C14E6 ethers were characterized by static (SLS) and dynamic light scattering (DLS) experiments to examine effects of uptake of n-octanol on the micellar characteristics. The SLS results have been successfully analyzed by the light scattering theory for micelle solutions to yield the molar mass Mw(c) as a function of concentration c along with the cross-sectional diameter d of the micelle. The apparent hydrodynamic radius RH,app(c) determined by DLS as a function of c has also been successfully analyzed by a fuzzy cylinder theory which takes into account the hydrodynamic and direct collision interactions among micelles, providing us with the values of the stiffness parameter lambda(-1). It has been found that the micellar length Lw increases with increasing surfactant weight fraction ws and increasing n-octanol content wo in the micelles or with raising temperature T. The values of d and lambda(-1) are found to increase with increasing wo, whereas the spacing s between hydrophilic tails of adjacent surfactant molecules on the micellar surface decreases with increasing wo. Comparison with our previous results for the C10E5 and C14E6 micelles containing n-dodecanol has revealed the salient features in change of the micellar characteristics with uptake of n-alcohols as follows: (i) The Lw values increase more significantly for the C14E6 micelles containing n-dodecanol than those containing n-octanol, whereas Lw of the C10E5 micelles increases by including n-dodecanol and n-octanol without a significant difference for the two alcohols. (ii) The values of d and lambda(-1) of the C10E5 and C14E6 micelles increase with uptake of n-octanol and n-dodecanol into the micelles. They are larger for the C10E5 micelles than for the C14E6 micelles, and their increase with alcohol content is less significant for the C14E6 micelles in comparison with the C10E5 micelles. (iii) The s values of the C10E5 and C14E6 micelles decrease with uptake of n-octanol and n-dodecanol into the micelles. They are somewhat larger in the latter micelles than in the former. (iv) The variation in d, s, and lambda(-1) with uptake of n-alcohol occurs with no difference in the effects for the two alcohols n-octanol and n-dodecanol.

Wormlike Micelles of Polyoxyethylene Alkyl Ethers CiEj

“…A series of the data points for the latter near w d ¼ 0:028 are the results by Hellweg and von Klitzing. 67 We find that at small w d , the cloud point curve shift to lower temperatures with increasing w d and then shift to higher temperatures at larger w d in contrast to the case of the micelle solutions containing n-alcohol [31][32][33][34][35] for which the phase boundaries monotonically shift to lower temperatures as the alcohol content increases. In panel a of Figure 25, the emulsification failure boundary schematically shown by the surface enclosed by dashed and dotted lines indicates that too much n-dodecane can not be included in the C 12 E 5 micelles at any T and w d .…”

“…They have shown that the apparent molar mass M app of the wormlike micelles formed in the L 1 phase increases with c in the range of small c, passing through a maximum, and then decreases with increasing c at higher c. Here, M app includes two contributions, i.e., concentration-dependent molar mass M w ðcÞ of the micelles and concentration dependent structure factor Sðc; q ¼ 0Þ (q the magnitude of scattering vector) which reflects thermodynamic interactions among micelles. We have also investigated solution properties of the wormlike micelles of various C i E j containing n-dodecanol, -octanol, and n-dodecane, [32][33][34][35][36][37] by applying the same technique as in the case of the micelles of C i E j and their mixtures described above.…”

“…[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] In the work, we have been able to determine the concentration-dependent characteristics of the micelles by separating contributions of the intermicellar thermodynamic and hydrodynamic interactions to the SLS and DLS results with the aid of the corresponding theories. We have determined the weight-average molar mass M w of the micelles as a function of surfactant mass concentration c along with the cross-sectional diameter d from the SLS data by using a molecular thermodynamic theory 21,38 formulated with the wormlike spherocylinder model.…”

“…The studies have been extended to the C i E j micelles containing n-dodecanol, n-octanol, and ndodecane in order to explore effects of uptake of n-alcohol and n-alkane into the micelles on the micellar characteristics. [31][32][33][34][35][36][37] The SLS and DLS results were successfully analyzed in a similar fashion to the micelle solutions of single C i E j and their binary mixtures.…”

Change in Characteristics of Wormlike Micelles of Hexaoxyethylene Tetradecyl and Decyl Ethers (C14E6 and C10E6) with Uptake of n-Dodecane

“…In this series of work on micelle solutions of nonionic surfactant polyoxyethylene alkyl ethers H(CH 2 ) i (OCH 2 CH 2 ) j -OH (abbreviated C i E j ), we have characterized the wormlike C i E j micelles with various i and j containing n-alcohols, ndodecanol or n-octanol, [1][2][3][4][5] and n-dodecane 6 by static (SLS) and dynamic light scattering (DLS) measurements in order to explore effects of uptake of n-alcohol or n-dodecane into the micelles on the micellar characteristics. It has been demonstrated that the SLS results (the excess Rayleigh ratio) as a function of surfactant concentration c are successfully analyzed by a molecular thermodynamic theory 7,8 formulated with the wormlike spherocylinder model to provide us with molar mass M w ðcÞ of the micelle at a specified c along with the crosssectional diameter d of the spherocylinder, as in the case of the micelle solutions of pure C i E j and binary C i E j mixtures.…”