Construction of a highly viscoelastic anionic wormlike micellar solution by carboxylate gemini surfactant with a p-dibenzenediol spacer

Abstract

Listen

Translate article

The viscoelastic wormlike micellar solutions formed by the carboxylate gemini surfactant, O,O′-bis(sodium 2-dodecylcarboxylate)-p-dibenzenediol (referred to as C12ϕ2C12), have been investigated by steady-state and dynamic frequency-sweep rheological techniques. Another system using its homologue, O,O′-bis(sodium 2-dodecylcarboxylate)-p-benzenediol (C12ϕC12), was also examined for comparison. Both C12ϕ2C12 and C12ϕC12 formed wormlike micelles without any additives. The C* corresponding to the onset of the semi-dilute regime was 48 mmol L−1 for C12ϕ2C12 and 160 mmol L−1 for C12ϕC12, respectively, showing the considerably high ability and efficiency of C12ϕ2C12 in forming wormlike micelles. The wormlike micelles started to entangle with each other at 60 mmol L−1 for C12ϕ2C12 and 300 mmol L−1 for C12ϕC12. The average length of the C12ϕ2C12 wormlike micelles was estimated to be about 1.0–1.9 μm, significantly longer than the C12ϕC12 ones. The solution viscosity of C12ϕ2C12 at 200 mmol L−1 reached 613 Pa s, much higher than 24.2 Pa s for C12ϕC12 at 500 mmol L−1. The mechanisms of forming wormlike micelles in both cases were revealed by dynamic light scattering measurements. Differently from the normal micellar growth that C12ϕC12 displayed, C12ϕ2C12 was found to form large network-like aggregates at very low concentrations. These aggregates could more conveniently transform into threadlike (wormlike) micelles by continuously increasing the concentration of C12ϕ2C12, from which a new approach was realised for highly viscoelastic anionic wormlike micellar solutions.