Electric field controlled formation and dissociation of multiwalled carbon nanotube (MWCNT) conductive pathways in a polycarbonate (PC) melt are investigated by the dynamic percolation measurement. The results show that field-induced MWCNT alignment causes the decrease in the activation energy of conductive pathway formation. The directional or disordered alignment of MWCNTs in the PC melt results in the transition from a conductor to an insulator as the electric field changes from 500 to 1 V/cm. This electric-controllable directional or disordered alignment technology is promising for the fabrication of low-dimensional conductive materials and applications of voltage-switch devices.

Conductive network formation and its dynamic process for multiwalled carbon nanotubes (MWNTs) and carboxyl-tethered MWNT (MWNT-COOH) filled poly(vinylidene fluoride)(PVDF) systems were investigated. Based on real-time tracing the variation of electrical resistivity of systems with isothermal treatment time, the conductive network formation was evaluated. It was found that the conductive network formation was temperature and time dependent. The percolation time, characterized at a certain annealing time where the electrical resistivity started to decrease drastically, decreased with the increase of the filler concentration or the annealing temperature. However, the values of the percolation time and the activation energy of conductive network formation for the PVDF/MWNT-COOH system were higher than those of the PVDF/MWNT system, indicating that the interaction between MWNTs and PVDF molecules played an important role in the conductive network formation of the composites. Furthermore, a modified thermodynamic percolation model was proposed to predict the percolation time of PVDF/MWNT composites. It was found that the calculated results fit the experimental data very well.

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The study of piezochromic materials (PCMs) has become an attractive field and numerous scholars have reported various material structures and phenomena. PCMs incorporating near‐infrared (NIR) emission have led to a broader range of applications due to the strong penetration and interference resistance of longer wavelength light sources. However, NIR PCMs are still rare due to difficulties in tuning molecular configuration, conformation and stacking structure. In this review, organic compounds are classified according to their types and structures, and recent advances in NIR PCMs are comprehensively summarized and described. The various factors affecting the piezochromic properties from the perspective of the compound structure are shown. The effects of pressure on the photophysical changes of different compounds are discussed. It is expected to provide ideas for subsequent NIR PCMs, from structural design to predicting their photophysical properties under pressure.

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