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A single-component photorheological fluid with light-responsive viscosity

DOI: 10.1039/C9NR10350C DOI Help

Authors: Elaine A. Kelly (University of Cambridge) , Niamh Willis-fox (University of Cambridge) , Judith E. Houston (European Spallation Source ERIC) , Camille Blayo (Trinity College Dublin) , Giorgio Divitini (University of Cambridge) , Nathan Cowieson (Diamond Light Source) , Ronan Daly (University of Cambridge) , Rachel C. Evans (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nanoscale , VOL 12 , PAGES 6300 - 6306

State: Published (Approved)
Published: March 2020
Diamond Proposal Number(s): 16235

Open Access Open Access

Abstract: Viscoelastic fluids whose rheological properties are tunable with light have the potential to deliver significant impact in fields relying on a change in flow behavior, such as in-use tuning of combined efficient heat-transfer and drag-reduction agents, microfluidic flow and controlled encapsulation and release. However, simple, single-component systems must be developed to allow integration with these applications. Here, we report a single-component viscoelastic fluid, capable of a dramatic light-sensitive rheological response, from a neutral azobenzene photosurfactant, 4-hexyl-4′butyloxymonotetraethylene glycol (C6AzoOC4E4) in water. From cryo-transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS) and rheology measurements, we observe that the photosurfactant forms an entangled network of wormlike micelles in water, with a high viscosity (28 Pa s) and viscoelastic behaviour. UV irradiation of the surfactant solution creates a less dense micellar network, with some vesicle formation. As a result, the solution viscosity is reduced by four orders of magnitude (to 1.2 × 10−3 Pa s). This process is reversible and the high and low viscosity states can be cycled several times, through alternating UV and blue light irradiation.

Subject Areas: Chemistry

Instruments: B21-High Throughput SAXS

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