Wormlike Micelles of Polyoxyethylene Alkyl Ethers CiEj

Abstract

It is demonstrated that wormlike micelles of nonionic surfactants polyoxyethylene alkyl ethers H(CH 2 ) i (OCH 2 CH 2 ) j OH (C i E j ) have been successfully characterized by static (SLS) and dynamic light scattering (DLS) measurements and viscometry with the aid of the theories developed so far in the field of polymer solution studies, i.e., a molecular thermodynamic theory for light scattering, chain statistical and hydrodynamic theories for semi-flexible polymers. The results for the excess Rayleigh ratio, radius of gyration, hydrodynamic radius, and intrinsic viscosity have been shown to be well represented by the theories based on a wormlike spherocylinder model. Some salient features found for the micelles of C i E j with various i or j, their binary mixtures, and the micelles including n-alcohol and n-alkane are discussed. The nonionic surfactant polyoxyethylene mono-alkyl ether H(CH 2 ) i (OCH 2 CH 2 ) j OH, (abbreviated C i E j ), exhibits a wide variety of phases in aqueous solution as a function of surfactant concentration and temperature. 1,2 Here, i and j denote the number of methylene groups in the alkyl group and that of repeating units in the oxyethylene group, respectively. At dilute regime, the C i E j + water binary system forms an isotropic phase, that is so-called L 1 phase, which consists of micelles formed with the amphiphilic molecules and water. The system exhibits the LCST behavior; the micellar solutions are phaseseparated into two phases at high temperatures. It is now well established that the micelles grow in size with increasing concentration and raising temperature, in particular to a greater extent when approaching the phase boundary, assuming threadlike or wormlike cylindrical shape. (See Figure 1.) The wormlike micelles have been visually shown by the cryo-TEM observation, 3 in which in the process of micellar growth, threadlike or polymer-like micelles are evolved in the solutions examined. The micelles are, thus, sometimes called ''living'' or ''equilibrium'' polymers in a sense that the linear macromolecules formed can break and recombine.The polymerlike micelles have certain similarities to real polymers and then their solution properties are analogous to those of real polymer solutions. They have been, thus, rather widely studied to characterize their shape and size by employing the theoretical concepts and experimental methods developped in the polymer solution studies, such as static (SLS) and dynamic light scattering (DLS), [3][4][5][6][7][8][9][10][11][12] small-angle neutron scattering (SANS), 13-15 viscometry, 15,16 pulsed-field gradient NMR, 4-7 and so forth. However, solutions of polymer-like micelles are essentially different from those of real polymers. The molar mass of the micelle, i.e., the aggregation number, varies with surfactant concentration, temperature, and other solvent conditions. The average value and distribution of the micellar size are determined by multiple chemical equilibrium among micelles with various aggregation numbers. Although the equi...

The synergistic steric hindrance effect in the preparation of polyether ether ketone composites by powder slurry method

“…The PEG molecules can self‐assemble in the solution to form Three‐dimensional network structure 44 . This has been confirmed in previous studies on other non‐ionic surfactants 45,46 . Therefore, the non‐Newtonian behavior of the suspension may relate to the particle disaggregation of the PEEK particles under high‐speed shear conditions in TX 47 .…”

“…44 This has been confirmed in previous studies on other non-ionic surfactants. 45,46 Therefore, the non-Newtonian behavior of the suspension may relate to the particle disaggregation of the PEEK particles under high-speed shear conditions in TX. 47 The shear thinning behavior of PEG, CS1, and CS2 is the result of particle disaggregation and WLMs interaction.…”

Prediction of Cloud Point Curves of Alkyl Ethoxylates with the Hydrophilic–Lipophilic‐Difference and Net‐Average‐Curvature (HLD‐NAC) Framework

“…However, in many applications including the formulation of cosmetics, oil, and concentrated cleaner solutions, the concentration of surfactant often surpasses 1 wt.% and thus elucidating cloud point curves of alkyl ethoxylates at various surfactant concentrations becomes critical to assess their efficiency. Furthermore, the cloud point phenomenon relates to conditions under which wormlike micelles form and influence the rheological behavior of these surfactant systems (Einaga, ).…”

Multiple Association–Dissociation Equilibria in Solutions of Amphiphilic Molecules

“…In aqueous solutions, surfactant molecules often form very long cylindrical micelles. − These micellar solutions exhibit characteristic properties resembling stiff-polymer solutions, for example, high viscosity, low diffusivity, and lyotropic liquid crystallinity. − However, solutions of cylindrical micelles and polymers are essentially different. The micelle size varies with the surfactant concentration, temperature, and other solvent conditions, in contrast with the polymer chain taking a fixed length.…”

“…Since the major component of P is the dimer, we consider only the case of the BLG dimer for simplicity (cf. eq ). The molar mass and ∂ n/ ∂ c of PR comprising two BLG molecules and n ′ + m ″ SDS molecules are given by Molar concentrations [P 2 U n ′+ m″ ] and [U m 0 ] necessary to calculate w i of the corresponding components by eq are calculated by along with eqs .…”