Density Functional Theory Study on the Mechanism of Nickel-Catalyzed 3,3-Dialkynylation of 2‑Aryl Acrylamides Via Double Vinylic C–H Bond Activation

The mechanisms of Ni-catalyzed 3,3-dialkynylation of 2-aryl acrylamide have been investigated by using density functional theory calculations. The result shows that this reaction includes double alkynylation, which involves sequential key steps of vinylic C–H bond activation, successive oxidative addition, and reductive elimination, with the second C–H bond activation being the rate-determining step. C–H and N–H bond activation occurs via the concerted metalation-deprotonation mechanism. The calculations show that no transition state exists in the first reductive elimination process, and a negative free energy barrier in the second reductive elimination process though a transition state is identified, indicating that the nickel-catalyzed vinylic C(sp2)–C(sp) bond formation does not require activation energy. Z–E isomerization is the prerequisite for the second alkynylation. In addition, our spin-flip TDDFT (SF-TDDFT) computational result discloses that the actual process of Z–E isomerization occurs on the potential energy surface of the first excited singlet state S1

Flexible Polydimethylsilane Nanocomposites Enhanced with a Three-Dimensional Graphene/Carbon Nanotube Bicontinuous Framework for High-Performance Electromagnetic Interference Shielding

High-performance electromagnetic interference (EMI)-shielding materials featuring lightweight, flexibility, excellent conductivity, and shielding properties, as well as superior mechanical robustness, are highly required, yet their development still remains a daunting challenge. Here, a flexible and exceptional EMI-shielding polydimethylsilane/reduced graphene oxide/single-wall carbon nanotube (PDMS/rGO/SWCNT) nanocomposite was developed by a facile backfilling approach utilizing a preformed rGO/SWCNT aerogel as the three-dimensional (3D) conducting and reinforcement skeleton. Pristine SWCNTs acting as secondary conductive fillers showed intriguing advantages, whose intrinsically high conductivity could be well preserved in the composites because of no surface acidification treatment. The robust and interconnected 3D network can not only serve as fast channels for electron transport but also effectively transfer external load. Accordingly, a prominent electrical conductivity of 1.2 S cm^–1 and an outstanding EMI-shielding effectiveness of around 31 dB over the X-band frequency range were achieved for the resultant composite with an ultralow loading of 0.28 wt %, which is among the best results for currently reported conductive polymer nanocomposites. Moreover, the composite displayed excellent mechanical properties and bending stability; for example, a 233% increment in the compression strength was obtained compared with that of neat PDMS. These observations indicate the unrivalled effectiveness of 3D rGO/SWCNT aerogel as a reinforcement to endow the polymer composites with outstanding conductive and mechanical properties toward high-performance EMI-shielding application

Flexible Polydimethylsilane Nanocomposites Enhanced with a Three-Dimensional Graphene/Carbon Nanotube Bicontinuous Framework for High-Performance Electromagnetic Interference Shielding

High-performance electromagnetic interference (EMI)-shielding materials featuring lightweight, flexibility, excellent conductivity, and shielding properties, as well as superior mechanical robustness, are highly required, yet their development still remains a daunting challenge. Here, a flexible and exceptional EMI-shielding polydimethylsilane/reduced graphene oxide/single-wall carbon nanotube (PDMS/rGO/SWCNT) nanocomposite was developed by a facile backfilling approach utilizing a preformed rGO/SWCNT aerogel as the three-dimensional (3D) conducting and reinforcement skeleton. Pristine SWCNTs acting as secondary conductive fillers showed intriguing advantages, whose intrinsically high conductivity could be well preserved in the composites because of no surface acidification treatment. The robust and interconnected 3D network can not only serve as fast channels for electron transport but also effectively transfer external load. Accordingly, a prominent electrical conductivity of 1.2 S cm^–1 and an outstanding EMI-shielding effectiveness of around 31 dB over the X-band frequency range were achieved for the resultant composite with an ultralow loading of 0.28 wt %, which is among the best results for currently reported conductive polymer nanocomposites. Moreover, the composite displayed excellent mechanical properties and bending stability; for example, a 233% increment in the compression strength was obtained compared with that of neat PDMS. These observations indicate the unrivalled effectiveness of 3D rGO/SWCNT aerogel as a reinforcement to endow the polymer composites with outstanding conductive and mechanical properties toward high-performance EMI-shielding application

Flexible Polydimethylsilane Nanocomposites Enhanced with a Three-Dimensional Graphene/Carbon Nanotube Bicontinuous Framework for High-Performance Electromagnetic Interference Shielding

High-performance electromagnetic interference (EMI)-shielding materials featuring lightweight, flexibility, excellent conductivity, and shielding properties, as well as superior mechanical robustness, are highly required, yet their development still remains a daunting challenge. Here, a flexible and exceptional EMI-shielding polydimethylsilane/reduced graphene oxide/single-wall carbon nanotube (PDMS/rGO/SWCNT) nanocomposite was developed by a facile backfilling approach utilizing a preformed rGO/SWCNT aerogel as the three-dimensional (3D) conducting and reinforcement skeleton. Pristine SWCNTs acting as secondary conductive fillers showed intriguing advantages, whose intrinsically high conductivity could be well preserved in the composites because of no surface acidification treatment. The robust and interconnected 3D network can not only serve as fast channels for electron transport but also effectively transfer external load. Accordingly, a prominent electrical conductivity of 1.2 S cm^–1 and an outstanding EMI-shielding effectiveness of around 31 dB over the X-band frequency range were achieved for the resultant composite with an ultralow loading of 0.28 wt %, which is among the best results for currently reported conductive polymer nanocomposites. Moreover, the composite displayed excellent mechanical properties and bending stability; for example, a 233% increment in the compression strength was obtained compared with that of neat PDMS. These observations indicate the unrivalled effectiveness of 3D rGO/SWCNT aerogel as a reinforcement to endow the polymer composites with outstanding conductive and mechanical properties toward high-performance EMI-shielding application

Flexible Polydimethylsilane Nanocomposites Enhanced with a Three-Dimensional Graphene/Carbon Nanotube Bicontinuous Framework for High-Performance Electromagnetic Interference Shielding

High-performance electromagnetic interference (EMI)-shielding materials featuring lightweight, flexibility, excellent conductivity, and shielding properties, as well as superior mechanical robustness, are highly required, yet their development still remains a daunting challenge. Here, a flexible and exceptional EMI-shielding polydimethylsilane/reduced graphene oxide/single-wall carbon nanotube (PDMS/rGO/SWCNT) nanocomposite was developed by a facile backfilling approach utilizing a preformed rGO/SWCNT aerogel as the three-dimensional (3D) conducting and reinforcement skeleton. Pristine SWCNTs acting as secondary conductive fillers showed intriguing advantages, whose intrinsically high conductivity could be well preserved in the composites because of no surface acidification treatment. The robust and interconnected 3D network can not only serve as fast channels for electron transport but also effectively transfer external load. Accordingly, a prominent electrical conductivity of 1.2 S cm^–1 and an outstanding EMI-shielding effectiveness of around 31 dB over the X-band frequency range were achieved for the resultant composite with an ultralow loading of 0.28 wt %, which is among the best results for currently reported conductive polymer nanocomposites. Moreover, the composite displayed excellent mechanical properties and bending stability; for example, a 233% increment in the compression strength was obtained compared with that of neat PDMS. These observations indicate the unrivalled effectiveness of 3D rGO/SWCNT aerogel as a reinforcement to endow the polymer composites with outstanding conductive and mechanical properties toward high-performance EMI-shielding application