Browsing by Author "Tabor, RF"

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    Design and synthesis of an azobenzene–betaine surfactant for photo-rheological fluids
    (Elsevier, 2021-07-15) Butler, CSG; King, JP; Giles, LW; Marlow, JB; Vidallon, MLP; Sokolova, AV; de Campo, L; Tuck, KL; Tabor, RF
    Hypothesis Morphology of surfactant self-assemblies are governed by the intermolecular interactions and packing constraints of the constituent molecules. Therefore, rational design of surfactant structure should allow targeting of the specific self-assembly modes, such as wormlike micelles (WLMs). By inclusion of an appropriate photo-responsive functionality to a surfactant molecule, light-based control of formulation properties without the need for additives can be achieved. Experiments A novel azobenzene-containing surfactant was synthesised with the intention of producing photo-responsive wormlike micelles. Aggregation of the molecule in its cis and trans isomers, and its concomitant flow properties, were characterised using UV–vis spectroscopy, small-angle neutron scattering, and rheological measurements. Finally, the fluids capacity for mediating particle diffusion was assessed using dynamic light scattering. Findings The trans isomer of the novel azo-surfactant was found to form a viscoelastic WLM network, which transitioned to inviscid ellipsoidal aggregates upon photo-switching to the cis isomer. This was accompanied by changes in zero-shear viscosity up to 16,000x.UV–vis spectroscopic and rheo-SANS analysis revealed interactions of the trans azobenzene chromophore within the micelles, influencing aggregate structure and contributing to micellar rigidity. Particles dispersed in a 1 wt% surfactant solution showed a fivefold increase in apparent diffusion coefficient after UV-irradiation of the mixture. Crown Copyright © 2021 Published by Elsevier Inc.
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    Fluorinated lamellar phases: structural characterisation and use as templates for highly ordered silica materials
    (Royal Society of Chemistry, 2014-05-13) Pottage, MJ; Tiara, K; Grillo, I; Garvey, CJ; Stickland, AD; Tabor, RF
    Highly ordered silica was synthesised by using a lamellar phase comprising the anionic fluorinated surfactant sodium perfluorooctanoate and the partially-fluorinated co-surfactant/oil 1H,1H,2H,2H-perfluorooctan-1-ol in water. The phase behaviour of this system was thoroughly analysed, and it was found that even low levels of the alcohol (<0.5 mol%) were sufficient to induce a phase change from normal micelles to a lamellar phase, rationalised as a result of geometric and electrostatic effects. The properties of these phases were compared to their hydrocarbon analogues, demonstrating the unique and valuable properties exhibited by fluorocarbons, directly related with the observed nanostructure. Small-angle neutron scattering was used to analyse the internal structure of the systems, providing information on the inter-lamellar spacing, bilayer thickness and membrane elasticity. The potential for these phases to act as shear-thinning lubricants was assessed using oscillatory rheology, obtaining shear-dependent viscosity along with storage and loss moduli.© 2014, The Royal Society of Chemistry.
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    Phase behavior, small-angle neutron scattering and rheology of ternary nonionic surfactant-oil-water systems: a comparison of oils
    (American Chemical Society, 2013-03-19) Tabor, RF; Zayeer, MI; Dagastine, RR; Grillo, I; Garvey, CJ
    The phase behavior of the nonionic surfactant Triton X-100 (polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether) was studied in two three-component systems: Triton-water-p-xylene and Triton-water-trichloroethylene. It was found that the aromatic solvent was able to produce monophasic soft matter systems at a significantly greater range of compositions. The structural characteristics of the phases generated were analyzed by small-angle neutron scattering, showing evidence for microemulsion, lamellar, and reverse-rnicroemulsion phases. In addition, for the Triton-water-p-xylene system, an L-3 "sponge" phase was found in a water-rich region of the phase diagram and the properties of this were examined using rheological measurements. The differences in phase behavior are discussed in light of the solvation properties of the surfactant in the different solvents studied. Most notably, xylene appears to favor phases with low-curvature interfaces, suggesting preferential solvation of the central phenyl group of Triton. © 2013, American Chemical Society.
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    Reversible pH- and photocontrollable carbohydrate-cased surfactants
    (Wiley Online Library, 2014-09-11) Tabor, RF; Tan, DD; Han, SS; Young, SA; Seeger, ZLE; Pottage, MJ; Garvey, CJ; Wilkinson, BL
    The parallel synthesis and properties of a library of photoswitchable surfactants comprising a hydrophobic butylazobenzene tail-group and a hydrophilic carbohydrate head-group, including the first surfactants to exhibit dual photo- and pH-responsive behavior, is reported. This new generation of surfactants shows varying micelle morphologies, photocontrollable surface tension, and pH-induced aggregation and adsorption. © 2014, WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Watching photo-sensitive surfactant micelles morph in real time using SANS
    (Australian Institute of Nuclear Science and Engineering, 2016-11-29) Tabor, RF; Wilkinson, BL; Garvey, CJ
    Recent interest has surged in colloidal and self-assembling systems that can respond to internal and external stimuli. Of the possible response mechanisms, light is seen as a clean and low energy ‘reagent’ for stimulating physical and chemical changes. We have recently synthesized a library of light-addressable surfactant molecules based around the photo isomerisable azobenzene core, coupled to sugar head-groups [1]. Depending on their molecular geometry, these molecules self-assemble into a wide variety of micellar structures, from small spheres to worms, fibres and liquid crystals, and the diversity of this self-assembly is uncovered using small-angle neutron scattering. By using time-resolved SANS, we can watch as the micelles change their shape in real time as the molecules undergo photo-isomerisation, pointing to applications in the delivery of sensitive cargoes, and the modulation of biological and cellular processes.
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    Wormlike micelle formation of novel alkyl-tri(ethylene glycol)-glucoside carbohydrate surfactants: Structure–function relationships and rheology
    (Elsevier, 2018-11-01) Moore, JE; Mccoy, TM; de Campo, L; Sokolova, AV; Garvey, CJ; Pearson, G; Wilkinson, BL; Tabor, RF
    Carbohydrates are appealing non-ionic surfactant head-groups as they are naturally abundant, generally biocompatible and biodegradable, and readily functionalized. Here, seven novel carbohydrate based surfactants (CBS) have been synthesized that contain a tri-ethylene glycol (TEG) linker between a glucose head-group and alkyl tail-group, with linear saturated (C8–18) and unsaturated (C18:1) alkyl chains. The aqueous adsorption and self-assembly of these surfactants was explored using tensiometry and small- and ultra-small-angle neutron scattering (SANS and USANS). With SANS we observed elongation from spherical to cylindrical micelles with increasing alkyl chain length. C16 and C18 chains exhibited pronounced Krafft points, yet formed worm-like micelles as single components upon heating to 43 and 48 °C respectively. The introduction of mono-unsaturation in the form of a C18:1 chain reduced the Krafft point and gave a surfactant that produced worm-like micelles in water without additives at room temperature. We also observed micellar elongation for C12 and C14 chains at 50 °C due to dehydration of the TEG linker. The room temperature worm-like micelles were further characterized using rheo-SANS and rheology, revealing the C18:1 surfactant to exhibit near ideal Maxwell behavior at low concentrations (2.9 wt.%). These results provide insight into structure-function relationships for CBS, and demonstrate a promising molecular candidate for the formation of viscoelastic worm-like micellar solutions. © 2018 Elsevier Inc.