Phase separation in polyelectrolyte gels
Fluids and Materials Seminar
3rd October 2024, 2:00 pm – 3:00 pm
Fry Building, Fry G.07
Polyelectrolyte gels are responsive fluid-filled solids used for soft robotics, drug delivery, and as model systems for biology. Polyelectrolyte gels are often surrounded by a salt solution. Small variations in the external salt concentration can trigger enormous and discontinuous changes in gel volume, a phenomenon called a volume phase transition. Using tools from dynamical systems, we reveal that the volume phase transition can occur via the formation of a travelling wave or spinodal decomposition within the gel, in agreement with experiments. Matched asymptotic expansions will then be used to resolve the thin electric double layer (EDL) that forms at the gel surface. We show that, despite its thinness, the EDL can drive a bulk flow in the external solution and a breakdown of electro-neutrality across the entire gel, which occurs through spatially localised modes of phase separation. The talk will conclude with a discussion of the bending of gel plates due to differential swelling and the need for a new, multi-scale modelling framework for polyelectrolyte gels.
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