Fabrication of semiconducting polyaniline-wrapped halloysite nanotube composite and its electrorheology

Modified halloysite nanotube filled polyimide composites for film capacitors: high dielectric constant, low dielectric loss and excellent heat resistance

In this work, halloysite nanotubes (HNTs) were chosen as the fillers and high performance polyimide (PI) as the matrix to form a series of dielectric composite materials with high dielectric constant, low dielectric loss and excellent heat resistance. Firstly, KH550 was used to modify the surface of HNTs to make sure of a good dispersion of HNTs into the polymer. The results showed that the addition of KH550 modified HNTs (K-HNTs) can improve the dielectric constant of the composite films while maintaining their excellent dielectric loss properties. To further increase the dielectric constant of the HNTs/PI composites, conductive polyaniline (PANI) was used to coat the surface of HNTs to obtain PANI modified HNTs (PANI-HNTs). Compared with the K-HNTs filled systems, the dielectric constant of the PANI-HNTs/PI nanocomposite films is greatly enhanced. The highest dielectric constant of the PANI-HNTs/PI films can achieve 17.3 (100 Hz) with a low dielectric loss of 0.2 (100 Hz). More importantly, the as-prepared composite films have high breakdown strengths (>110.4 kV mm-1) and low coefficients of thermal expansion, as low as 7 ppm per °C, and a maximum discharge energy density of 0.93 J cm-3. Also, such properties are maintained stably up to 300 °C, which is critical for manufacturing heat-resisting film capacitors.

Polymeric Nanoparticle-Coated Pickering Emulsion-Synthesized Conducting Polyaniline Hybrid Particles and Their Electrorheological Study

To produce an electric stimuli-responsive electrorheological (ER) material, semiconducting core/shell-type polyaniline (PANI) hybrid particles were fabricated through Pickering emulsion-type polymerization, using poly(divinylbenzene-alt-maleic anhydride) (PDVMA) particles as a solid surfactant. The PDVMA nanoparticles were initially polymerized using a self-stable precipitation method. The fabricated PANI/PDVMA composite particles were subjected to various chemical characterizations; further, they were suspended in silicone oil at 10 vol % to prepare an ER fluid, and their viscoelastic behaviors were scrutinized using a rheometer under various input electric fields. We also adopted an LCR meter to evaluate its dielectric characteristics. Our results showed that the PANI/PDVMA composite particles display typical ER performance, such that both dynamic and elastic yield stresses follow a polarization mechanism with a slope of 2.0.

Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields

This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER) behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particular focus is given to the electro-responsive ER characteristics of the polymer/clay nanocomposites in terms of the yield stress and viscoelastic properties along with their applications.