Building Efficient 3D Networks by Controlled Localization of Hybrid Fillers in Immiscible Polymer Blends

Controlling filler localization is essential, yet not easy, when building a synergistic 3D conductive network of fillers with different sizes and shapes in multiphase polymer blends. We herein report on preparing polymer composites with double-percolated structures of controlled filler localization from an immiscible polymer blend of poly(ethylene-co-octene) (POE) and poly(butylene adipate-co-terephthalate) (PBAT). The 2D microscale graphite flakes (FGs) exhibit distinct dispersion behaviors from their 1D nanoscale analogue, carbon nanotubes (CNTs). CNTs are observed in the PBAT phase independent of the mixing sequences, while FGs reside in their predispersing matrix. An "auto-sieving" effect on CNTs and FGs is observed when the fillers are predispersed in POE and compounded with PBAT. In contrast, double-percolated structures with filler hybridization in a single phase can be obtained by predispersing CNTs and FGs in POE and PBAT, respectively. Specifically, CNTs predispersed in POE migrate to PBAT, where FGs are located, and produce a double-percolated structure that hybridizes the fillers in the PBAT phase. The hybridization of FGs and CNTs in the PBAT phase results in a 3D network with enhanced interconnectedness for superior electrical and thermal conduction. These composites can be transformed into those with hybrid segregated conductive networks and superior electromagnetic wave shielding effectiveness after solvent extraction to remove the PBAT phase.