Engineering New Ion-Conducting Membranes using Tapered Block Polymers

Ion-conducting block polymers have enormous potential for membrane applications such as lithium battery separator/electrolytes due to their ability to form ordered and co-continuous nanostructures.  These self-assembling macromolecules can allow the simultaneous control over ionic transport, processing, and mechanical strength, thus providing an enticing opportunity toward fabricating designer polymer electrolytes for flexible, lightweight, and efficient devices.  From the standpoint of increasing processability in polymer electrolytes, tapered block polymers provide an efficient way to decouple processing temperatures from the polymer molecular weight by reducing interfacial interactions between pure blocks through adjustments in the interfacial composition; in other words, the order–disorder transition temperatures (T_ODT) and glass transition temperatures can be tuned independent of molecular weight and overall block composition using tapered interfaces.  Recently, we have successfully synthesized a tapered block polymer electrolyte system that shows significantly improved room temperature lithium ion conductivity, co-continuous nanoscale network structures, lower temperature processability, robust cycling behavior, and lower energetics associated with lithium ion motion.  This behavior can be correlated directly to the composition of the tapered interfaces in our modified block polymers, and these tapered architectures may demonstrate similar advantages in other nanostructured polymer systems.