Effects of polymer end groups on the drying rates of phase separating coatings

The effect of chain end groups on the drying of phase separating polymer blends was investigated for different functionally terminated poly(dimethyl siloxane) (PDMS). The drying rates of a PDMS/cellulose acetate butyrate (CAB) blend in methyl ethyl ketone (MEK) or isopropyl acetate (IA) were measured using the gravimetric method. The weight loss curves revealed that the addition of dihydroxyl-terminated PDMS significantly increased the drying rate in a particular range of solvent concentrations. On the contrary, monoglycidyl-ether-terminated and monohydroxyl-terminated PDMS showed suppressed evaporation and particular transitions between suppressed and enhanced drying modes, respectively. The drying enhancement was especially observed in cases where the separating polymer domains were developed through a film, regardless of the surface activities of PDMS. These facts imply that the interfaces between the domains act as diffusion paths for solvent molecules, and thus guide the transportation of solvent from the interior to the surface.