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An isotactic polypropylene (iPP) nanocomposite with low percolation threshold, ultrahigh dielectric permittivity and toughness by controlling the dispersion of multi-walled carbon nanotubes (MWCNTs) through ethylene-α-octene block copolymer (OBC), is reported. A special ‘sosatie’ structure, i.e. finely dispersed long MWCNTs inserted in OBC phase uniformly distributed in the continuous iPP matrix, was constructed through simple melt compounding process. The percolation threshold of the prepared iPP/OBC/MWCNT nanocomposites was ca. 0.5 vol%, lower than that of iPP/MWCNT nanocomposites. The iPP/OBC/MWCNT nanocomposites exhibited an ultrahigh dielectric permittivity (ca. 9000) at 100 Hz and a very low dielectric loss (ca. 1.5). MWCNTs also improved the compatibility between iPP and OBC components, leading to a high impact strength of iPP/OBC/MWCNT nanocomposites (about 13 times higher than pure iPP when the content of MWCNT was 1.49 vol%). Thus, the approach reported in this work can provide a new and convenient route to prepare high-performance polymer nanocomposite dielectric materials with low percolation thresholds and balanced mechanical properties. [ABSTRACT FROM AUTHOR]

Most stretchable film strain sensors generally present nonlinear electrical responses to applied strain, leading to an inaccurate acquisition of sophisticated signals, difficult signal processing, and zero‐calibration, which hampers practical applications severely. Here, a Janus hetero‐structured microarray film sensor is developed by in‐situ growth of silver nanoparticles on the surface of micro‐patterned elastomer films fabricated via low‐temperature imprinting followed by scraping‐induced particle trapping. Heterogeneous property designs in both modulus and electrical conductivity via introducing polymer microarrays enable modulating the electron transport manner in the conductive layer of elastic Janus films upon stretching, allowing to tune signal linearity effectively. Therefore, such a hetero‐structured film sensor shows good signal linearity (fluctuation of gauge factor [GF] below ±0.02) and relatively high sensitivity (GF > 10) within 55% strain, a detection limit of 0.2% strain, and a response/recovery time of 16.3/46.9 ms, respectively. Correspondingly, it enables monitoring human respiration and body motion with higher resolution compared with the nonlinear one, meanwhile, it is capable of detecting tiny pressure to discriminate braille alphabets via touch identification. Overall, it unveils a simple strategy to fabricate film strain sensors for high‐resolution healthcare and body motion monitoring, as well as electronic skins toward tactile sensing and touch identification. [ABSTRACT FROM AUTHOR]

Stretchable electrodes play a crucial role in wearable electronics for high-efficiency carrier transport in the information communication, yet it is challenging to achieve high electrical conductivity at large strain for stretchable and porous conductive composites. Here, a simple yet efficient strategy is proposed to fabricate highly conductive, porous and stretchable composites via seeding hydrophilic carbon nanotube (CNT) oil-in-water microemulsions in elastomer films prior to growing silver nanoparticles (AgNPs) in situ. It aims at forming a dual heterogeneous structure of CNT microspheres in the elastomeric films containing conductive networks of AgNPs, which allow to guarantee the overall good electrical conductivity. Unlike the rapid propagation of cut-through microcracks in conventional conductive network of AgNPs under strain, the mechanical and electrical dual hetero-structured CNT microspheres in the conductive networks can sustain high electrical conductivity at large strains by blocking and cutting off microcrack propagation. Therefore, the porous composite electrodes show electrical conductivity above 103 S/cm at 200% strain thanks to the efficient dissipation of strain energy by dual hetero-structured CNT microspheres, which is controlled by CNT concentration in the oil-in-water microemulsions. Besides, the as-fabricated porous composites sustain high yet stable electrical conductivity at various kinds of mechanical deformations, such as tension, bending, twisting and a combination of them, allowing for the promising application in stretchable and wearable electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]