We present a novel strategy for the fabrication of ordered and flexible polymer-based graphene foams by self-assembly of graphene sheets on a 3D polymer skeleton. The obtained graphene foams show excellent mechanical, electrical, and hydrophobic properties, thus holding great potential as elastic conductors and oil-water separators.
Polymer-based materials with a high dielectric constant show great potential for energy storage applications. Since the intrinsic dielectric constant of most polymers is very low, the integration of carbon nanotubes (CNTs) into the polymers provides an attractive and promising way to reach a high dielectric constant owing to their outstanding intrinsic physical performances. However, these CNT-based composites usually suffer from high dielectric loss, low breakdown strength and the difficulty to tailor the dielectric constant. Herein, we have designed and fabricated a new class of candidates composed of graphene oxide-encapsulated carbon nanotube (GO-e-CNT) hybrids. The obtained GO-e-CNT-polymer composites not only exhibit a high dielectric constant and low dielectric loss, but also have a highly enhanced breakdown strength and maximum energy storage density. Moreover, the dielectric constant of the composites can be tuned easily by tailoring the loading of GO-e-CNTs. It is believed that the GO shells around CNTs play an important role in realizing the high dielectric performances of the composites. GO shells can not only effectively improve the dispersion of CNTs, but also act as insulation barriers for suppressing leakage current and increasing breakdown strength. Our strategy provides a new pathway to achieve CNT-based polymer composites with high dielectric performances for energy storage applications.
The incorporation of graphene sheets (GSs) into polymer matrices affords engineers an opportunity to synthesize polymer composites with excellent physical performances. However, the development of high performance GS-based composites is difficult because of the easy aggregation of GSs in a polymer matrix as well as the weak interfacial adhesion between GSs and the host polymer. Herein, we present a simple and effective route to hyperbranched aromatic polyamide functionalized graphene sheets (GS-HBA). The resulting GS-HBA exhibits uniform dispersion in a thermoplastic polyurethane (TPU) matrix and strong adhesion with the matrix by hydrogen-bond coupling, which improve the load transfer efficiency from the matrix to the GSs. Thus, the GS-HBA-TPU composites possess excellent mechanical performance and high dielectric performance. It has been demonstrated that the GS-HBA composite has higher modulus, higher tensile strength and higher yield strength, and remains at nearly the same strain at break when compared with the composites with graphene oxide, ethylene diaminemodified graphene, and hydrazine reduced graphene. In addition, the hyperbranched polymer chains allow construction of a large number of microcapacitors and suppress the leakage current by isolating the GSs in a TPU matrix, resulting in a higher permittivity and lower loss tangent for the GS-HBA composite in comparison with ethylene diamine-modified graphene, or hydrazine reduced-graphene composites.
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