In a study that may have an impact on redispersibility of powders in water, the wetting of polymer layers by polar solvents has been studied. As known before, when a droplet of solvent spreads on a substrate, both the contact angle and the spreading velocity decrease with time as solvent is taken up by the substrate. In the study, it is shown that when the substrate is initially glassy, the contact angle may decrease steeply, and that this variation is related to glass transition due to the solvent uptake.

(Dupas, J., Verneuil, E., Van Landegheim, M., Bresson, B., Forny, L., Ramaioli, M., Lequeux, F., Talini, L., Phys. Rev. Lett. 112, 188302, published 6 May 2014)