Wetting of polymers by their solvents

Abstract

We review the studies on the wetting of soluble polymeric substrates by their solvents, both in the literature and conducted in our group in the past decade. When a droplet of solvent spreads on a soluble polymer layer, its wetting angle can strongly vary with the contact line velocity even at capillary numbers smaller than unity, in contrast to non-soluble substrates. The solvent content in the polymer is a key parameter for the spreading dynamics; that content is set by the initial conditions, but also by the transfers occurring from the droplet to the polymer layer during spreading. We focus on hydrophilic amorphous polymers that are glassy at room temperature, and we discuss the consequences on wetting of the very large changes in the polymer physical properties induced by solvent sorption. We finally present new results on polymers of varying molar masses, and show how they open new perspectives for a better understanding of powder dissolution.

Understanding the role of molar mass and stirring in polymer dissolution

“…Polymer powder dissolution in a solvent is generically described using three different steps: 27 first, polymer grains sprinkled at the solvent surface must be wetted by the solvent, what can be very slow. 28 Second, grains must be dispersed in the bulk solvent so as to obtain individual grains surrounded by solvent. 29 The third step, namely the swelling and erosion of individual grains, has been semi-quantitatively described in the present paper, both in still water and under stirring, using simple scaling laws.…”

Reconstitution of Food Powders Granulated with Oil‐in‐Water Emulsions

“…In our analysis we did not measure the displacement velocity of the advancing front line, which is known to affect the magnitude of the advancing angle , because our analysis was limited only to a rough comparison with the equilibrium contact angle for the choice of the best operating conditions. For the same reason we did not consider the effect of the initial water activity of the different food ingredients which is also known to have an effect on the advancing contact angle , .…”

Evaporation of water droplets on photoresist surfaces – An experimental study of contact line pinning and evaporation residues

“…The modes of interaction of solvent droplets with polymer layers have been studied in detail. [1][2][3][4] Transport can occur inside the polymer matrix by diffusion or outside by evaporation, recondensation or sorption. The polymer material and transport properties typically depend very sensitively on the local solvent concentration.…”