Rapid Vertical Ordering of Lamellar Block Copolymer Films by Dynamic Thermal Gradient Annealing for Ion Conduction Membranes

To achieve the full technological potential of block copolymers (BCPs) for use as electrolytes, filtration membranes, or in nanolithography, rapid ordering of BCPs with vertically oriented nanostructures on unmodified substrates is desirable. In this work, we demonstrate the rapid ordering of lamellar BCPs (< 40 s) by utilizing the effect of thermal gradient based Cold Zone Annealing (CZA) technique. The evaporation fronts during film casting results in poorly ordered yet vertically oriented BCP morphology. We demonstrate that CZA, by driving in-plane defect annihilation in such vertically oriented as cast BCP nanostructures, resulted in perpendicularly oriented and well-ordered morphology on a variety of substrates, at short time scales. The kinetics of lamellar grain size (x) evolution was observed to be much faster in CZA (x ~ t^0.26) as compared to oven annealing (x ~ t^0.15). Subsequent post-annealing integration of Ionic liquid (IL) as a penetrating additive was shown to selectively swell well-ordered lamellar domain by 100%, having potential use for mechanically robust ion-conducting channels in BCP membranes and electrolytes. Such highly swollen and vertically ordered lamellar nanostructures are not obtained by a priori addition of IL to BCP solutions before film casting.