Tuning structure and properties of lamellar sulfonated pentablock terpolymer films

Thin films of sulfonated block copolymers are widely studied for applications in water purification and electrochemical devices. When films are cast from solution, the ultimate structures are strongly influenced by the solvent’s polarity. These structures are often not well-defined, presenting a challenge for fundamental studies of structure and properties. In this work, we demonstrate lamellar self-assembly in 16-µm films of a sulfonated pentablock terpolymer cast from solvent mixtures. As the polarity of the solvent mixture is increased, the lamellar structure becomes more disordered. Both surface and bulk properties are impacted by these changes: the surface becomes more hydrophilic, and water uptake increases by a factor of 1.5. This increase in water uptake comes at the expense of mechanics, as the films become tacky and disintegrate over time in water. These results demonstrate that continuity of the sulfonated domains can be tuned through processing. The knowledge acquired from this work can facilitate structure-property-processing relations of these highly complex materials.