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 +...