Dr. Simon Titmuss

I am a Reader in the School of Physics & Astronomy at the University of Edinburgh, which I joined in 2010. My current research interests focus on the application of polymer physics to biological problems and the development of more sustainable materials. Many of these problems involve drying of complex fluids, such as polymer solutions and blood, and how they imbibe into porous materials, such as fabrics. I really enjoy the opportunity to work with industrial partners via the Edinburgh Complex Fluids Partnership to solve challenging industrial problems.

Evaporation of Concentrated Polymer Solutions is Insensitive to Relative Humidity

Abstract: Evaporation of water from polymer solutions is ubiquitous in many processes in nature and industrial coatings. By measuring the mass-loss from polymer solutions contained in open-ended capillaries we were able to demonstrate that the evaporation is insensitive to the ambient relative humidity (RH) up to RH≈80%. The evaporation rate transitions from being constant at early times, as is the case for pure water, to decreasing as ~1/√t. This behaviour is consistent with the formation of a polarisation layer of concentrated polymer at the interface with the ambient environment. The behaviour at higher RH and the observation of a non-zero evaporation rate in steady state indicate that stress in the interfacial layer plays a role in determining the evaporative dynamics. I will discuss comparison with phase field modelling and briefly comment on what happens if the polymer is a polyelectrolyte. These results may prove significant for the evaporation of pathogen-containing respiratory droplets, which also include gel-forming macromolecules, as well as for optimizing industrial coatings.

[1] Max Huisman, Paul Digard, Wilson Poon & Simon Titmuss, Phys. Rev. Lett. 131 (2023) 248102

[2] Max Huisman, Wilson Poon, Patrick Warren, Simon Titmuss & Davide Marenduzzo, Soft Matter 21 (2025) 1508-1515