| 초록 |
In drying films of polymer-colloid mixtures, the stratification where polymers are placed on top of larger colloids is studied. It is often presumed that the formation of segregated polymer-colloid layers is solely due to the proportion in size at fast evaporation. By comparing experiments with a theoretical model, we found that the transition in viscosity near the drying interface was another important parameter for stratification in polymer-colloid mixtures. At high evaporation rates, increased polymer concentrations near the surface lead to a phase transition from semidilute to concentrated regime, where colloidal particles are kinetically arrested. Stratification only occurs if the formation of a stratified layer precedes the evolution to the concentrated regime near the drying interfaces. Otherwise, the colloids will be trapped by the polymers in the concentrated regime before forming a segregated layer. Our findings are relevant for developing solution-cast polymer composite for painting, antifouling and antireflective coatings. |
