Cambridge scientist shares latest insights into photoswitchable surfactants

FigureA scientist from the University of Cambridge visited the University of Sheffield to present her work on the self-assembly and structure-function relationships of photoswitchable surfactants.

Students and staff in the Department of Chemistry were the first audience to hear about this research, which aims to shine a light on how these materials can be used to acquire photoswitchable viscosity.

Dr Evans was appointed a lecturer at Cambridge in 2017, and is chair of the Royal Society of Chemistry Photophysics and Photochemistry group. She was elected a Fellow of the Royal Society of Chemistry in 2018 and was invited by Dr Seb Spain to give a talk on some of her recent work in Sheffield

The talk began with a well-known example of a photoswitchable structure, in the form of azobenzene. This molecule normally exists in its trans state, but can be photoswitched to its cis form using 360 nm light. By incorporating this azo group into the tail of a surfactant, one can obtain a photoswitchable surfactant – dubbed AzoPS.

The rest of Dr Evans' talk discussed how her group have investigated the microstructure of these surfactants at different concentrations, using a variety of intricate techniques, and how these structures change upon application of light, including an in-situ spectroscopic study.

A key finding was that in the trans form, some of these AzoPS systems exist as entangled networks, which are non-Newtonian fluids and therefore highly viscous. However in the cis form, they become much more like water. Thus, by simply applying ultraviolet light, you can easily and reversibly photoswitch the viscosity of these surfactants!

After the talk, Dr Evans said: "As this is a relatively new field for us, this was the first opportunity I have had to present our new findings in detail. Fortunately the Sheffield crowd were very friendly and asked some great questions!"