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Instruments / Technical Area	Publication Details	Published
B21-High Throughput SAXS	Light-responsive self-assembly of a cationic azobenzene surfactant at high concentration Camille Blayo , Elaine A. Kelly , Judith E. Houston , Nikul Khunti , Nathan P. Cowieson , Rachel C. Evans Soft Matter 56 DOI: 10.1039/D0SM01512A Diamond Proposal Number(s): [13867] Open Access Show Abstract ▼ Abstract: The formation of high-concentration mesophases by a cationic azobenzene photosurfactant is described for the first time. Using a combination of polarised optical microscopy and small-angle X-ray scattering, optically anisotropic, self-assembled structures with long-range order are reported. The mesophases are disrupted or lost upon UV irradiation.	Oct 2020
B21-High Throughput SAXS	A single-component photorheological fluid with light-responsive viscosity Elaine A. Kelly , Niamh Willis-fox , Judith E. Houston , Camille Blayo , Giorgio Divitini , Nathan Cowieson , Ronan Daly , Rachel C. Evans Nanoscale 12, 6300 - 6306 DOI: 10.1039/C9NR10350C Diamond Proposal Number(s): [16235] Open Access Show Abstract ▼ 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.	Mar 2020
B21-High Throughput SAXS	Multimodal control of liquid crystalline mesophases from surfactants with photoswitchable tails Judith E. Houston , Elaine A. Kelly , Margarita Kruteva , Kiriaki Chrissopoulou , Nathan Cowieson , Rachel C. Evans Journal Of Materials Chemistry C 51 DOI: 10.1039/C9TC04079J Diamond Proposal Number(s): [16235] Open Access Show Abstract ▼ Abstract: Non-invasive manipulation of the hierarchical structure of functional materials is a key challenge in the advancement of optoelectronics, energy conversion and storage devices and drug delivery systems. Lyotropic liquids crystals, with their long-range order and a rich array of structures, have long been exploited as soft templates to prepare porous materials. The potential to modify the template structure using an external stimulus such as light could lead to new architectures. Here, using a combination of small-angle X-ray scattering and polarised optical microscopy, we decipher the various structure/self-assembly relationships of neutral surfactants bearing photoswitchable tails, which self-organise into a rich variety of lyotropic liquid crystalline mesophases. Facile, multimodal control of the nanoscale morphology of these single-component systems is achieved through: (i) molecular structure, via careful selection of the alkyl tail/ethylene oxide headgroup lengths; (ii) concentration; (iii) temperature; and (iv) photoisomerisation. The nanoscale architectures range from the weakly concentrated hyperswollen lamellar phases, the more common lyotropic lamellar and hexagonal phases, to pure thermotropic liquid crystals; all of which are accessible at room temperature. Photoisomerisation with UV light leads to the reversible destruction of the liquid crystalline phase, which can be spatially controlled through the use of a mask. This extensive study demonstrates the versatility of neutral photosurfactants and paves the way for new applications, such as photoresponsive templates or drug delivery systems.	Aug 2019

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