Structured block copolymer thin film composites for ultra-high energy density capacitors*

Development of high energy density capacitors is essential for future applications like hybrid vehicles and directed energy weaponry. Fundamentally, energy density is governed by product of dielectric permittivity $\varepsilon $ and breakdown strength V$_{bd}$. Hence, improvements in energy density are greatly reliant on improving either $\varepsilon $ or V$_{bd}$ or a combination of both. Polymer films are widely used in capacitors due to high Vbd and low loss but they suffer from very low permittivities. Composite dielectrics offer a unique opportunity to combine the high $\varepsilon $ of inorganic fillers with the high V$_{bd}$ of a polymer matrix. For enhancement of dielectric properties, it is essential to improve matrix-filler interaction and control the spatial distribution of fillers for which nanostructured block copolymers BCP act as ideal templates. We use Directed Self-assembly of block copolymers to rapidly fabricate highly aligned BCP-TiO2 composite nanostructures in thin films under dynamic thermal gradient field to synergistically combine the high $\varepsilon $ of functionalized TiO2 and high V$_{bd}$ of BCP matrix. The results of impact of BCP morphology, processing conditions and concentration of TiO2 on capacitor performance will be reported.