Wormlike Micelles of Hexaoxyethylene Decyl C10E6 and Tetradecyl C14E6 Ethers Containing n-Dodecanol

Abstract

ABSTRACT:Wormlike micelles formed with the surfactant hexaoxyethylene decyl C 10 E 6 and tetradecyl C 14 E 6 ethers were studied by static (SLS) and dynamic light scattering (DLS) experiments to examine variation of the micellar characteristics with uptake of n-dodecanol. The SLS results have been analyzed by the light scattering theory for micelle solutions to yield the molar mass M w ðcÞ as a function of concentration c along with the cross-sectional diameter d of the micelle. The apparent hydrodynamic radius R H,app ðcÞ determined by DLS as a function of c is also successfully analyzed by a fuzzy cylinder theory which takes into account the hydrodynamic and direct collision interactions among micelles, allowing us to evaluate the stiffness parameter À1 . It has been found that the micellar length increases with increasing surfactant weight fraction w s or with raising temperature T irrespective of the composition of n-dodecanol content in the micelles. The length of the micelles at fixed w s and T steeply increases with increasing weight fraction w d of n-dodecanol. The length of the C 14 E 6 micelles is extremely larger than that of the C 10 E 6 micelles. In the previous work on micellar solutions of nonionic surfactant polyoxyethylene alkyl ethers H(CH 2 ) i (OCH 2 CH 2 ) j OH (abbreviated C i E j ) and their binary mixtures, we have studied characteristics of the micelles by static (SLS) and dynamic light scattering (DLS) measurements and viscometry. [1][2][3][4][5][6][7][8][9] It has been demonstrated that the SLS results (Rayleigh ratios) as a function of surfactant concentration are well represented by a molecular thermodynamic theory 10,11 formulated with the wormlike spherocylinder model to yield the values of M w ðcÞ at a specified surfactant concentration c along with the cross-sectional diameter d of the micelles. The molar mass M w dependence of the mean-square radius of gyration hS 2 i, hydrodynamic radius R H , and intrinsic viscosity [] is quantitatively represented by the chain statistical 12 and hydrodynamic 13-16 theories based on the wormlike chain and spherocylinder models, respectively, thereby providing us with the values of the stiffness parameter À1 . Following the work, We have also studied C 12 E 6 , C 10 E 5 , and C 12 E 5 micelles containing n-dodecanol to explore effects of uptake n-alcohol into the micelles on the micellar characteristics. [17][18][19] It has been then found that the SLS and DLS results are successfully analyzed as in the case of the micelle solutions of simple C i E j or their binary mixtures. In particular, it has been demonstrated that the fuzzy cylinder theory [20][21][22] is applied in a favorable way to analyze the apparent hydrodynamic radius R H,app as a function of the micelle concentration, thereby obtaining the concentration-dependent micellar growth by separating contributions of the enhancement of hydrodynamic interactions among micelles.The present work extends the studies to micelles in the C 10 E 6 + n-dodecanol + water and C 14 E 6 + ndodecanol +...

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

“…The d values of these micelles increase with increasing n-dodecane content w d in the micelles. The present results are similar to the previous findings for the C i E j micelles containing n-dodecanol or n-octanol [3][4][5] and also those containing n-dodecane. 6 They are also in qualitative agreement with SANS results by Menge et al 32 for C 12 E 5 micelles containing n-decane.…”

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.…”