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• The ordered oriented BN/BNNT heterostructure was constructed by the interface engineering strategy. • The consecutive dual-channel phono transmission paths were constructed in PAI composites. • The prepared PAI composite film exhibits ultrahigh thermal conductivity and excellent mechanical flexibility. Thermal conductive polymeric materials have aroused increasing attention as thermal management materials in the field of intelligent electronic devices due to their intriguing advantages. However, the discontinuity of phonon transmission path construction represents the bottleneck for thermal conductivity enhancement of composite materials, which limits the practical application of composite materials. Herein, flexible polyamide-imide (PAI) thermally conductive composite films with hierarchical structure composed of synergistically assembled functionalized boron nitride nanosheets (FBN) and polydopamine (PDA)-modified boron nitride nanotubes (FBT) by layer-by-layer assembly strategy are constructed. Benefitting from the optimized interface engineering with the ordered oriented arrangement FBN/FBT filler structure, the obtained composite film with optimized hybrid filler contents exhibits the super high thermal conductivity of 71.1 W·m−1·K−1, prominent thermal conductivity enhancement as high as 3663 % and excellent mechanical flexibility. The introduction of FBT can further expand the thermal contact area attributed to its inherent high thermal conductivity and aspect ratio. Additionally, the consecutive dual-channel phono transmission paths can be constructed in PAI composites under the synergistic action of FBN and FBT, further improving the phonon transmission density and suppressing phonon scattering, which endows PAI composite films with excellent thermal conductivity under low load of filler. The resulting multifunctionalities make the PAI composite films promising for flexible intelligent wearable electronic devices as thermal management materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Interconnected graphene/carbon fiber network was constructed by the co-carbonation process for functional integration of composites. • The composites obtained both excellent EMI shielding performance (∼73 dB) and good thermal conductivity (1.65 W·m-1·K-1). • The all-carbon network endows the polyimide composites with light-weight and environmental-friendly advantages. With the rapid development of electronic information and technology, materials with electromagnetic interference (EMI) shielding and thermal management are playing an increasingly important role in the semiconductor industry. However, the strategy of synthesizing the above dual-functional materials remain a challenge. Herein, the interconnected graphene/carbon fiber networks constructed by a facile co-carbonation strategy was reported to obtain the polyimide composites with EMI shielding properties and thermal conductivity (TC). The composite exhibited superior EMI shielding of ∼ 73 dB at the thickness of 2 mm when the carbon network content is 20 wt%. Moreover, the through-plane TC of the composite reaches 1.65 W·m−1·K−1, which is 611% higher than that of polymer matrix. We attribute the increased EMI shielding and TC properties to the construction of graphene/carbon fiber co-carbonation network, which provides an efficient and continuous electric conductive and thermally conductive network in the polyimide matrix. Moreover, the co-carbonation network can increase the polarization loss of electromagnetic waves while decreasing the interfacial thermal resistance between fillers. The structural–functional integration strategy is helpful for developing new high-performance dual-functional composites for the electronics and aerospace industries. [ABSTRACT FROM AUTHOR]

The highly thermally conductive yet electrically insulating polymeric materials are exhibiting tremendous potential for thermal management materials. However, the practical application of these materials is restrained by the limited thermal conductivity (TC) and deterioration of mechanical properties. In this work, an ultraflexible polyamide-imide (PAI) film with a sandwich-like structure composed with assembled well-oriented functionalized boron nitride nanosheets (FBN) by facile layer-by-layer solution-coating strategy is constructed. The design of the layered structure and highly oriented arrangement of interconnected FBN (Herman's orientation parameter ƒ up to 0.847) endows the obtained PAI composite film with super-flexibility, ultrahigh in-plane thermal conductivity (λ //), superior thermal transfer capability (ΔT max = 24.4 °C) and excellent electrical insulation performance. The PBP composite film reaches an ultrahigh λ // of 45.7 W m−1 K−1 with only 23 wt% FBN loading and exhibits a remarkable TC enhancement factor over 23 because of the more continuous phonon transfer networks that constructed by interconnected well-oriented FBN which could effectively suppress the phonon scattering. Furthermore, the mechanical properties of the layered composite film (PB4P) exhibit noteworthy enhancement compared with uniform PBN composite film, in which the tensile strength is increased by 110% and toughness enhancement is 329%. Meaningfully, our fabrication strategy has the advantage of simplicity and adaptability for commercial amplification. The composite film developed in this work provides a promising prospect for the thermal management system of modern power electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon-based polymer composites with excellent thermal conductivity are highly desired in thermal management materials. However, the thermal conductivity enhancement of carbon-based polymer composites is limited, which are mostly caused by defects of fillers, unsatisfactory distribution and inferior interface between carbon fillers and matrix. Herein, we prepared polyamide composites with three-dimensional (3D) vertically aligned carbon network. The vertically aligned structure demonstrates a through-plane thermal conductivity up to 1.45 W m−1 K−1 at 5.2 wt% carbon fillers content, which is 644% higher than that of matrix. Moreover, through the regulated surface modification of carbon fillers, the carbon fiber with lower defect density and improved interfacial compatibility were obtained. The vertically aligned structure could take advantage of the intrinsic properties of carbon fillers and effectively reduce thermal contact resistance. The fabricated polyamide composites could be employed to dissipate excessive heat in thermal management system, and effectively reduce the working temperature of CPU. The design principles and preparation techniques in this work could also be applied to other carbon-based composites to surmount difficulties in effective thermal management of modern electronics. [ABSTRACT FROM AUTHOR]

Chemical functionalization of boron nitride (BN) is necessary to improve the dispersion of the BN as well as interface compatibility within polymer matrix to enhance the properties of their composites. However, the degree of BN functionalization needs to be considered comprehensively to fully highlight the advantages. In the present work, a polyamide-imide (PAI) film with a parallel arrangement structure and designed functionalization of BN nanosheets by self-assembly technique is constructed. The design of optimum functionalization and defect control of the functionalized BN nanosheets (f-BNNSs) provides this flexible PAI/f-BNNSs composite film exhibits highly in-plane thermal conductivity, superior electrically insulating and improved mechanical properties. The thermal conductivity of the PAI/f-BNNSs film had an impressive improvement of 167%, from 5.06 W m−1 K−1 of PAI/BN film to 13.5 W m−1 K−1 of PAI/f-BNNSs film (PP1W3) at a low filler content of only 9 wt%. More importantly, systematic research was carried out in terms of the degree of functionalization, the quantities of defect of f-BNNSs and the performance of the composite films, which further revealed the mechanism of the thermal conductivity improvement of PAI/f-BNNSs composite films. This research provides significant guidance for the design of composite materials with excellent thermal conductivity based on the functionalization of low dimensional fillers, ensuring its application in the thermal management of high-power density electronic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermal conductive polymer matrix composites are becoming more widely used in modern electronic devices. However, the dispersion of the filler in the composite material limits the improvement of its heat dissipation performance. In order to solve the problem, we prepared polyamide-imide composites with three-dimensional (3D) carbon fiber-graphene network. The network is built by braided frame of carbon fiber felt and the hydrogen bonding between carbon fiber and graphene oxide. When the amount of filler is 4.25 wt%, the vertical thermal conductivity (TC) of composites reaches 0.53 W m−1 K−1, which is 165% higher than that of pure PAI. The improvement of TC is mainly attributed to the following factors, for example, 1) the 3D carbon fiber-graphene network structure was established to construct the heat conduction path in the composite material; 2) the interaction between fillers reduced contact thermal resistance; 3) the introduction of oxygen-containing functional groups adversely affected the TC of the composite. Meanwhile, the tensile strength of the composites reaches 34.1 MPa and the Young's modulus is 1.2 GPa. The composites can be used as a heat sink for next-generation electronic devices. Polyamide-imide composites are fabricated using three-dimensional (3D) carbon fiber-graphene network. The network is built by braided frame of carbon fiber felt and the hydrogen bonding between carbon fiber and graphene oxide. When the amount of filler is 4.25 wt%, the vertical thermal conductivity (TC) of composites reaches 0.53 W m−1 K−1, which is 165% higher than that of pure PAI. Image 1 [ABSTRACT FROM AUTHOR]

Polymeric composites with excellent thermal conductivity are in high demand in modern electronics because of their need for efficient heat dissipation. Whereas, the thermally conductive polymeric composites usually be limited by the insufficient effectiveness of the thermally conductive pathway, at the cost of high filler content and deterioration of mechanical strength. At the same time, they lack multi-functionality. Here, we reported advanced thermoresponsive polymeric composites containing a three-dimensional interconnected boron nitride (BN) network, which simultaneously displayed high thermal conductivity enhancement, thermal transfer performance, improved shape memory, and mechanical properties. Manufactured composites on the basis of commercial polyurethane sponges which were modified by polydopamine and coated with BN through dip-coating assemble method and the subsequent vacuum infiltration. The composites exhibit 2.4 W•m−1•K−1 with 17.5 wt% BN loading, and the through-plane thermal conductivity enhancement reaches 1100%. Furthermore, the mechanical properties of the composites have improved four times compared with pure polyethylene glycol. The obtained composites demonstrate the strong application in thermal management and were simulated in the CPU of the computer. Our fabrication provides a promising strategy to achieve multi-functional polymeric composites through constructing a three-dimensional thermally conductive pathway. [Display omitted] • The composites with 17.5 wt% BN exhibits excellent TC enhancement of 1100%. • The mechanical properties of the composites have improved 4 times. • The composites show application in thermal management which could comparable to Cu. • The composites show combined enhanced TC, mechanical and shape memory properties. [ABSTRACT FROM AUTHOR]