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    Branched alkyldimethylamine oxide surfactants: An effective strategy for the design of high concentration/low viscosity surfactant formulations

    Year: 2019

    Journal: J. Colloid Interface Sci., Volume 552, SEP 15, page 448–463

    Authors: Fabozzi, Antonio; Krauss, Irene Russo; Vitiello, Rosa; Fornasier, Marco; Sicignano, Luca; King, Stephen; Guido, Stefano; Jones, Christopher; Paduano, Luigi; Murgia, Sergio; D'Errico, Gerardino

    Keywords: Zwitterionic surfactants; Branched tail; Concentrated formulation; Phase diagram; Humidity-scan quartz crystal microbalance with dissipation (QCM-D); Rheology

    Hypothesis: The rational design of branched-tail surfactants is a suitable strategy to obtain low-viscosity surfactant-rich isotropic aqueous mixtures with negligible effects on biodegradability. This opens a way to the design of concentrated (water-free) surfactant formulations, highly attractive for their ecological and economic benefits. Experiments: The aggregation behaviour of N,N-dimethyl-2-propylheptan-1-amine oxide (C(10)DAO-branched) in aqueous mixtures is investigated across the entire composition range by polarized optical microscopy, small angle X-ray and neutron scattering, electron paramagnetic resonance, and pulse-gradient stimulated echo nuclear magnetic resonance. The humidity scanning quartz crystal microbalance with dissipation monitoring technique is validated as a tool for the fast screening of surfactants phase behaviour. Furthermore, the shear viscosities and viscoelastic moduli of the systems are determined by rheological measurements. Findings: With respect to the linear isomer, C(10)DAO-branched presents a much lower tendency to form lyotropic liquid crystalline phases. Except for a narrow composition and temperature range in which a lamellar structure is observed, C(10)DAO-branched aqueous mixtures are isotropic liquids whose microstructure changes, with increasing concentration, from micellar solutions to unstructured dispersions of hydrated surfactant molecules. Low-viscosity was found for all these mixtures, including the most concentrated ones. Thus, the introduction of a single short side-chain in the tail is demonstrated to be an effective approach to increase the active concentration in surfactant formulations. (C) 2019 Elsevier Inc. All rights reserved.
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