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Developing polymer dielectrics with a low dielectric loss but high dielectric permittivity (ε′) and breakdown strength (Eb) is steadily expected for applications in microelectronic and electrical industries. In this study, to elevate the overall dielectric properties of molybdenum (Mo)/poly(vinylidene fluoride) (PVDF), an insulating polystyrene (PS) shell was first constructed on the Mo's surface through a suspension polymerization, and then the core-shell Mo@PS particles were compounded with the host PVDF. The PS shell's influence on the dielectric performances of the composites was explored in terms of the filler concentration, diverse shell thicknesses and frequency. Compared with neat Mo/PVDF, the Mo@PS/PVDF composites present immensely restrained loss and conductivity owing to the insulating PS interlayer stopping the physical contact among Mo powder and wonderfully constraining the long-range charges migration. More importantly, the integrated dielectric performances can be efficaciously tuned and optimized via engineering the PS shell's thickness because the PS shell not only bolsters the interfacial interactions, but also alleviates the local electric field distortion and concentration subsequently leading to boosted Eb. Analyzing the dielectric results via the Havriliak-Negami expression theoretically illustrates the underlying polarization mechanism in the composites. The resulting Mo@PS/PVDF composites owing high ε′ and Eb coupled with fairly low loss, present prospective applications in electrical power systems. [ABSTRACT FROM AUTHOR]

Polymer dielectrics have received increasing attention owing to their wide applications in electrical, microelectronic and energy storage fields. However, it remains a challenging to prepare polymer dielectrics with a high dielectric constant (ε) but low dissipation factor (tanδ). In this work, conductive molybdenum (Mo) particles were encapsulated by a thin layer of semi-conductive molybdenum trioxide (MoO3) with a wide bandgap of 3.28 eV via a facile thermal calcination way under air, and the gained core–shell structured Mo@MoO3 particles were composited with poly(vinylidene fluoride) (PVDF) to generate morphology-controllable high-ε but low loss composites. The large ε can be realized in the PVDF composites with the Mo@MoO3, and both the electric conductivity and tanδ of the composites are significantly restrained to rather low levels even at high filler loadings, and apparently decrease with increasing the MoO3' shell thickness. The significantly ameliorated dielectric performances can be ascribed to the presence of MoO3 interlayer preventing the Mo particles from direct contact with each other and simultaneously hindering the long-range electron migration. The developed Mo@MoO3/PVDF composites with a high ε but low loss are great potential applications for electrical industries and microelectronic industries. [ABSTRACT FROM AUTHOR]

Exploring polymer composites with a high dielectric constant (ε′) and breakdown strength (Eb), low dissipation factor (tanδ), as well as a high thermal conductivity (TC) is of crucially important thanks to their potential applications in modern electronics. Herein, in this paper, two kinds of core–shell-structured Si particles, i.e., Si@SiO2, Si@SiO2@PS, were prepared by high temperature oxidation and polystyrene (PS) coating and incorporated into PVDF (poly(vinylidene fluoride)). The results indicate that both the fillers' kinds and loading have obvious influences on dielectric and thermal properties of the composites. The SiO2 interlayer between the Si and PVDF matrix remarkably suppresses the loss and reduces leakage conductivity, whereas encapsulation of Si@SiO2 with a PS shell further inhibits the loss and conductivity, and the organic PS interlayer enhances the interfacial compatibility and promotes the fillers' homogeneous dispersion in PVDF, therefore improving the Eb of the composites. More importantly, the PVDF composites with 50 wt.% of Si@SiO2@PS show good comprehensive performances: ε′ of 66.6 but tanδ of 0.04 at 100 Hz, Eb of 2.48 kV/mm as well as a high TC of 1.0 W/m K. The prepared Si@SiO2@PS/PVDF composites show promising potential applications in microelectronics and electrical industries. [ABSTRACT FROM AUTHOR]

Polymer dielectrics with super dielectric constant (ε'), low loss as well as high thermal conductivity (TC) are gaining tremendous momentum owing to the ever-increasing demands on microelectronic devices. Introduction core–shell fillers into polymers has been demonstrated as a promising strategy for high-ε' but low loss. Herein, nickel (Ni) particles were encapsulated by an insulating layer of NiO with various thicknesses via controlling calcination times at 550 °C under air, and the as-prepared core–shell Ni@NiO was incorporated into poly(vinyli-dene fluoride) (PVDF). The results verify the formation of a NiO shell outside of the Ni, and manifest that the PVDF with Ni@NiO particles exhibit a high ε', a signally suppressive loss and conductivity, as well as a high-TC compared with raw Ni. The reason can be ascribed to multiple effects of NiO interlayer including the enhancement of interface compatibility and interface polarizations and the blocking of leakage current. Furthermore, the thickness of NiO shell exerts different influences on long-range and short-range charge migration, and it should be rationally tuned to optimize the dielectric properties and TC. This study provides an effective idea to regulate and control the dielectric properties and TC of polymer composites. [ABSTRACT FROM AUTHOR]

Purpose: Low-dose metronomic (LDM) chemotherapy represents a new strategy to treat solid tumors by stronger antiangiogenic activity and less side effects. The aim of the study is to rationally develop a docetaxel metronomic regimen in preclinical settings of gastric cancer. Methods: In vitro cell proliferation, apoptosis, and thrombospondin-1/vascular endothelial growth factor (TSP-1/VEGF) expression analyses were performed on human umbilical vein endothelial cells (HUVECs) and gastric cancer (BGC-823) cells exposed for 144 h to metronomic concentrations of docetaxel. BGC-823 human gastric cancer xenograft model was used, and tumor growth and side effects were closely monitored. Quantitative real-time PCR was used to determine TSP-1/VEGF mRNA levels in tumor samples. Expression of VEGF and CD31 was observed by immunohistochemistry. Results: Our results indicated that LDM docetaxel preferentially inhibited HUVEC cell proliferation and induced HUVEC apoptosis. Docetaxel significantly increased TSP-1 expression and secretion in HUVEC cells whereas the expression and secretion of VEGF significantly decreased in BGC-823 cells. LDM docetaxel significantly inhibited BGC-823 tumor growth in the absence of toxicity, which was accompanied by decreases in microvessel density (MVD) and VEGF and increases in TSP-1 gene expression in tumor tissues. Conclusions: In vitro results show the antiangiogenic properties of LDM docetaxel. In vivo, LDM docetaxel treatment is effective against gastric tumor and microvessel growth without toxic effect on nude mice. [ABSTRACT FROM AUTHOR]