Polymer blends with enhanced dielectric properties enabled by rationally designed chain-packing behavior: a computational study

Controlling nanostructure in polymers is important for many applications. For polymer dielectrics, rational nanostructure design may increase the energy storage capacity by enhancing either the dielectric constant or the dielectric breakdown strength. In our previous studies, we showed that by blending polymers with different periodicities, the dielectric constant can be enlarged due to free-volume expansion. In this work, we use molecular dynamics with classical force fields to simulate polymer blends with different morphologies, including extended and coiled chains. The results show that polyimide (PI) and polyetherimide (PEI) are miscible and tend to form extended blend structures instead of coiled blobs. Consequently, the polymer chains are packed closer and nano voids are dramatically reduced. The increased packing can significantly boost the dielectric breakdown strength and lead to greatly increased electric energy density in capacitor structures. The theoretical results are in very good agreement with experimental data [1].
[1]. Q-Y. Zhang, X. Chen, B. Zhang, T. Zhang, W. Lu, Z. Chen, Z. Liu, B. Donovan, R. J. Warzoha, E. D. Gomez, J. Bernholc, Q. M. Zhang, to be published.