Drying kinetics of colloid-polymer suspensions confined in a two-dimensional geometry

We investigated the drying behavior of aqueous colloid-polymer suspensions using three different polyvinyl alcohols (PVAs) of various molecular weights (Mws). The dissolved polymer molecules were transported and accumulated around the drying interface. The accumulation was more dominant in the smaller PVAs. A packed layer of particles formed during drying. The small molecules were able to permeate the voids in the packed particles more easily. The rate of water evaporation decreased dramatically as the concentration of dissolved PVA near the drying interface (Cedge) increased. Although the Cedge increased more rapidly when we used smaller PVAs, the rate of water evaporation was not affected by the Mw. The decrease in the rate of water evaporation was smaller from a polymer solution without colloidal particles than it was from the colloid-polymer suspensions. We conclude that the accumulation of dissolved polymer molecules in the narrow voids of packed particles impedes water evaporation during drying. The drying kinetics of the water disturbed by the PVAs in the packed particles will be discussed.