Structure and dynamics of poly(oxyethylene) cholesteryl ether wormlike micelles: Rheometry, SAXS, and cryo-TEM studies

Rekha Goswami Shrestha*, Ludmila Abezgauz, Dganit Danino, Kenichi Sakai, Hideki Sakai, Masahiko Abe

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

In this article, we provide direct evidence for 1-D micellar growth and the formation of a network structure in an aqueous system of poly(oxyethylene) cholesteryl ether (ChEO20) and lauryl diethanolamide (L-02) by rheometry, small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (cryo-TEM). The ChEO20 self-assembles into spheroid micelles above the critical micelle concentration and undergoes a 1-D microstructural transition upon the incorporation of L-02, which because of its lipophilic nature tends to be solubilized into the micellar palisade layer and reduces the micellar curvature. The elongated micelles entangle with each other, forming network structures of wormlike micelles, and the system shows viscoelastic properties, which could be described by the Maxwell model. A peak observed in the zero-shear viscosity (η0) versus L-02 concentration curve shifted toward higher L-02 concentrations and the value of maximum viscosity (η0 max) increased with the increasing ChEO20 mixing fraction with water. We observed that η 0 max increased by 2 to 4 orders of magnitude as a function of the ChEO20 concentration. The Maxwell relaxation time (τR) shows a maximum value at a concentration corresponding to η0 max (i.e., τR increases with L-02 concentration and then decreases after attaining a maximum value, whereas the plateau modulus (G0) shows monotonous growth). These observations demonstrate microstructural transitions in two different modes: L-02 first induces 1-D micellar growth and as a result the viscosity increases, and finally after the system attains its maximum viscosity, L-02 causes branching in the network structures. The microstructure transitions are confirmed by SAXS and cryo-TEM techniques.

Original languageEnglish
Pages (from-to)12877-12883
Number of pages7
JournalLangmuir
Volume27
Issue number21
DOIs
StatePublished - 1 Nov 2011
Externally publishedYes

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