Wormlike micelles of pentaoxyethylene tetradecyl ether C14e 5 and hexaoxyethylene hexadecyl ether C16e6

Abstract

Micelles of pentaoxyethylene tetradecyl C14E5 and hexaoxyethylene hexadecyl C16E6 ethers in dilute aqueous solutions were characterized by static (SLS) and dynamic light scattering (DLS) experiments at several temperatures T between the LCST and UCST phase boundaries. The SLS results were successfully analyzed with the aid of the thermodynamic theory formulated with wormlike spherocylinder model for SLS of micelle solutions, yielding the molar mass Mw of the micelles as a function of concentration c and the cross-sectional diameter d. The radius of gyration (S2)1/2 of the micelles as a function of M w was found to be well described by the corresponding theories for the wormlike chain model. Combining the present and previous results for various CiEj (polyoxyethylene alkyl ether) micelles, effects of the hydrophobic (alkyl) i and hydrophilic (oxyethylene) chain length j on the micellar characteristics have been clarified as: (i) The weight-average micellar length Lw becomes larger for larger i and smaller j. (ii) The d values do not significantly vary with the values of i and j. (iii) The stiffness parameter λ-1 decreases with increasing i at fixed j and increases with increasing j at fixed i.