Interlayer decoration of expanded graphite by polyimide resins for preparing highly thermally conductive composites with superior electromagnetic shielding performance

Polymer-based conductive composites are promising thermal management and electromagnetic interference (EMI) shielding materials that are highly desired in modern integrated electronics and fifth-generation mobile communication technology, yet remain extremely challenging to fabricate (e. g., homogeneous dispersion of nanofillers, construction of continuous conductive network and formation of strong interfacial interaction, etc). Herein, we report a strategy to boost the thermal conduction and EMI shielding properties of polyimide (PI) -based composites by constructing large-size aligned graphite sheets inside PI matrix. The main steps includes initial self-assembly of PI microspheres into the interlayer space of polydopamine-modified expanded graphite (EG-PDA), subsequent decoration of interlayer space of EG-PDA by PI resins via microspheres melting and permeating, and the final hot pressing densification. In this way, the large-sized graphite sheets consisted of lateral van-der-Waals (vdW)-bonded and oriented graphite nanosheets within the composites can form consecutively conductive pathways, which together with the enhanced interface affinity between PI and EG-PDA via hydrogen-bonding synergistically improve the in-plane thermal conductivity to an optimum value of 65.6 W m(-1) K-1 with outstanding EMI shielding effectiveness of 101 dB at filler loading of 60 wt%. In addition, the high thermal conductivity and EMI shielding performance can be retained after being subjected to combustion or chemically corrosive environments, and in repeated processing, revealing broad prospects in the fields of next -generation electronic devices.