Flexible Polydimethylsiloxane Composite with Multi-Scale Conductive Network for Ultra-Strong Electromagnetic Interference Protection

Abstract

Highlights:

1. A multi-scale conductive network was constructed in flexible PDMS/Ag@PLASF/CNT composite with micro-size Ag@PLASF and nano-size CNT.

2. The PDMS/Ag@PLASF/CNT composite showed outstanding electrical conductivity of 440 S m^-1 and superior electromagnetic interference shielding effectiveness of up to 113 dB.

3. The PDMS/Ag@PLASF/CNT composites owned good retention (> 90%) of electromagnetic interference shielding performance even after subjected to a simulated aging strategy or 10,000 bending-releasing cycles.

Abstract: Highly conductive polymer composites (CPCs) with excellent mechanical flexibility are ideal materials for designing excellent electromagnetic interference (EMI) shielding materials, which can be used for the electromagnetic interference protection of flexible electronic devices. It is extremely urgent to fabricate ultra-strong EMI shielding CPCs with efficient conductive networks. In this paper, a novel silver-plated polylactide short fiber (Ag@PLASF, AAF) was fabricated and was integrated with carbon nanotubes (CNT) to construct a multi-scale conductive network in polydimethylsiloxane (PDMS) matrix. The multi-scale conductive network endowed the flexible PDMS/AAF/CNT composite with excellent electrical conductivity of 440 S m⁻¹ and ultra-strong EMI shielding effectiveness (EMI SE) of up to 113 dB, containing only 5.0 vol% of AAF and 3.0 vol% of CNT (11.1wt% conductive filler content). Due to its excellent flexibility, the composite still showed 94% and 90% retention rates of EMI SE even after subjected to a simulated aging strategy (60 °C for 7 days) and 10,000 bending-releasing cycles. This strategy provides an important guidance for designing excellent EMI shielding materials to protect the workspace, environment and sensitive circuits against radiation for flexible electronic devices.

Supplementary Information: The online version contains supplementary material available at 10.1007/s40820-022-00990-7.

Keywords: Carbon nanotube; Electromagnetic interference shielding; Flexible conductive polymer composites; Multi-scale conductive network; Silver-plated polylactide short fiber.

Fig. 1

a Schematic illustration of the fabrication process for AAF and the digital photograph of AAF; SEM images of b, f PLASF, c, g treated PLASF, d, h AAF; e TGA curves of PLASF and AAF; i Ag elemental mapping image of AAF

Fig. 2

a Schematic illustration of the fabrication process of PAAC composites; b digital photographs of AAF (left), CNT (middle), AAF/CNT mixture in the n-heptane (right); c XRD curves of PLASF, AAF, CNT and the composites containing AAF or CNT; d-f SEM images of PAA3C3; g the POM image and h, i TEM images of PAA3C3 composites with different magnification; j, k EDS images of PAA3C3 composites

Fig. 3

a The electrical conductivity of the PAAC composites with different AAF and CNT contents; b, c EMI SE of PAAC composites with various single-filled AAF and CNT contents in the X-band; the EMI SE of d PAAxC1, e PAAxC2, f PAAxC3 composites in the X-band frequency range; the absorption loss (SE_A) and reflection loss (SE_R) of g PAAxC1, h PAAxC2 and i PAAxC3 composites in the X-band frequency range

Fig. 4

The reflection coefficient (R), absorption coefficient (A) and transmission coefficient (T) at 10.0 GHz for a PAAxC1, b PAAxC2, c PAAxC3 composites; d EMI SE, e SE_A and SE_R of PAA5C3 composite with different thicknesses; f EMI SE of PAA5C3 composite before and after bending-releasing cycles with the insets showing a bending-releasing cycle; g the compression strain–stress curves of PAA5C2 composite at various strains; h Digital photograph illustrating the compression state (left) and the diameter change of the composite (right); i EMI SE of PAA5C2 composite before and after compression (load: 5 kg) at 60 and 100 °C

Fig. 5

a Schematic illustration of transmission loss of EM waves across the PAAC composite with the multi-scale conductive network; b Comparison of EMI SE of PAAC composite and previously reported EMI shielding composites with different thicknesses and conductive filler contents. WPU, PLA, TSM, PP, CB, rGO, PVDF, MXene, GF, PANI, SA, CuNWs, TAGA, PC, EMA, GCNT, PA6, EG, MS, TPU, PIL, PMMA and SEBS represent waterborne polyurethane, poly(lactic acid), temperature-sensitive microspheres, polypropylene, carbon black, reduced graphene oxide, poly(vinylidene fluoride), metal carbides/nitrides/carbonitrides, graphene foam, polyaniline, sodium alginate, copper nanowires, thermally annealed graphene aerogel, polycarbonate, ethylene–methyl acrylate, Graphene-MWCNT hybrid filler, polyamide 6, expanded graphite, melamine sponge, thermoplastic polyurethane, polymerizable ionic liquid copolymer, polymethyl methacrylate, poly (styrene-b-ethylene-ran-butylene-b-styrene), respectively