No abstract

No abstract

A small amount of carbon nanotubes (CNTs) was added into poly(vinylidene fluoride) (PVDF)/boron nitride (BN) composites through melt blending processing. The thermal conductivity, microstructure changes including the crystallization behavior of PVDF matrix and the dispersion states of fillers in the composites, and the electrical conductivity of the composites were comparatively investigated. The results demonstrated that compared with the PVDF/BN composites at the same BN content, the ternary PVDF/BN/CNT composites exhibited largely enhanced thermal conductivity. In the PVDF/BN/CNT composites, the crystallinity of the PVDF matrix was slightly increased while the crystal form remained invariant. BN particles exhibited homogeneous dispersion in the PVDF/BN composites, and they did not affect the rheological properties of the PVDF/BN composites when the BN content was lower than 10 wt %. The presence of CNTs did not affect the interfacial adhesion between BN and PVDF, but they facilitated the formation of denser BN/CNT network structure in the composites. The mechanisms were then proposed to explain the largely enhanced thermal conductivity of the PVDF/BN/CNT composites. Furthermore, the dielectric property measurements demonstrated that the PVDF/BN/CNT composites containing relatively low BN content exhibited a high dielectric constant with a low dielectric loss. This endowed the PVDF/BN/CNT composites with a greater potential application in the field of electronic devices.

An ultrathin polyurethane/MXene flexible nanocomposite film with synergistic mechanical properties and superior electromagnetic interference shielding is fabricated via a nacre-mimetic strategy.

Stretchable sensors are essential for flexible electronics, which can be made with polymer elastomers as the matrix. The main challenge in producing practical devices is to obtain polymers with mechanical stability, eco-friendliness, and self-healing properties. Herein, we introduce urea bonds and 2ureido-4[1H]-pyrimidinone (UPy) to synthesize tailored waterborne polyurethanes (WPU-UPy-x) with a hierarchical hydrogen bond (H-bond). Accordingly, sound tensile performance (strength: 53.33 MPa, toughness: 128.97 MJ m −3 ), satisfying deformation recovery, and good self-healing capability of the WPU-UPy-x film are demonstrated. With atomic force microscope characterization, we find that UPy groups contribute to the highly improved microphase separation of WPU-UPy-x, responsible for good mechanical properties. As a proof of concept, a strain sensor is successfully configured, thanks to the good interfacial interactions between the polyurethane matrix and the Ti 3 C 2 T x MXene conductive filler, which features sensitive and stable performance for monitoring diverse human and mechanical motions. Intriguingly, this sensor is capable of self-healing after cutting and displays well-retained sensitivity to detect the stretched signal. The as-proposed design concept for healable and sensitive strain sensors can shed light on future wearable electronics.

A new kind of PCMs have been fabricated through the MF and CNF co-mediated assembly of GNPs, and the PCMs exhibit excellent performances, with great potential applications in many fields relating to energy conversion, storage, release and utilization.

In this work, the binary blend of poly(ethylene vinyl acetate) (EVA)/poly(ε-caprolactone) (PCL) with different compositions were prepared and the shape memory behaviors were evaluated first. Then, carbon nanotubes (CNTs) were introduced into the composition that exhibited relatively better shape memory effect (SME) to prepare the ternary blend composites with electrically actuated SME. The morphologies of the blend and/or blend composites, the crystallization of the component, and the selective location states of CNTs in the blend composites were comparatively investigated. The results demonstrated that the binary EVA/ PCL blends exhibit a typical sea−island structure at low PCL content, a quasi-cocontinuous structure at mediate PCL content and then the sea−island structure at high PCL content. Among these binary blends, the EVA/PCL (60/40) sample exhibits relatively better SME with not only high shape fixing ratio but also shape recovery ratio. The presence of the CNTs further induces the changes of morphology and crystallization behavior in the blend composites. Due to the largely reduced electrical resistivity promoting more Joule heat generation at applied voltage, the blend composites containing relatively high content of CNTs exhibited excellent electrically actuated SME. This work demonstrated that introducing CNTs into the immiscible blends and controlling the selective location of CNTs in one component, the electrically actuated SME could be achieved at relatively lower voltage and the shape recovery speed could also be greatly increased.

Achieving a desirable combination of good mechanical properties and healing efficiency is a great challenge in the development of self-healing elastomers. Herein, a class of tough and strong self-healing polyacrylate elastomers (denoted as HPs) was developed simply by free-radical copolymerization of n-butyl acrylate (nBA) and tert-butyl acrylate (tBA) and a subsequent hydrolysis reaction rather than direct copolymerization of nBA and acrylic acid (AA). The tiny difference in reactivity between nBA and tBA makes the structural units of the copolymer easy to control. Precise regulation of molecular composition can be realized just by varying the relative monomer content, making its mechanical properties to vary from ductile to robust. Strikingly, when HP samples are cut off within the gauge length, they can heal into coherent and smooth samples and recover at least 79% of the original strength. Hydrogen bond interactions serve as physical cross-linking points, contributing to the high mechanical performance (fracture energy of up to 73.78 MJ·m–3 and tensile strength of up to 17.80 MPa) as well as shape memory function. Moreover, the HP samples emit strong fluorescence when exposed to a 365 nm UV lamp and exhibit an aggregation-enhanced emission effect in the state of dissolution.