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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]

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]

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]

Emerging structural materials for aerospace deformable structures, soft robotics, and advanced smart electronic devices necessitate reversible, lockable, and reprogrammable shape transformation capabilities. A challenge in this realm is heat accumulation in high-power density devices, which limited impedes broader applications of these materials. This study introduces magneto-thermal coupling response and efficient heat dissipation to structural composite, facilitating reversible and reprogrammable material deformation. Our composites prepared using bi-directional freeze casting strategy demonstrated excellent thermal management capabilities. When the composites were applied to the chip heat dissipation, the chip temperature was significantly reduced by 36.3 °C from 112.2 °C. Furthermore, the integration of a flexible boron nitride nanosheets (BNNS)/carbon fibers (CFs) network with magnetic Fe 3 O 4 particles and phase-change material enables effective magneto-thermal response. This magnetically controlled thermal deformation behavior of composites provides a promising avenue for the development of multimodal morphing structures for soft robotics and aerospace applications. [ABSTRACT FROM AUTHOR]

Thermal conductive and electrical insulating polymer composites are showing tremendous potential for modern electrical systems and electronic devices. Melt blending has been utilized as an effective technique to prepare thermal interface materials. However, during the process of melt-blending, strong π-π stacking and particle aggregation may be caused by thermal heating and local mechanical stress. Herein, ISP-PA6/BNNSs-OH (ISP-PN) composite has been fabricated by a masterbatch obtained via in-situ polymerization (ISP) and melt blending with polyamide-6 (PA6), with the incorporation of hydroxylated boron nitride nanosheets (BNNSs-OH). At the filler loading of 10 wt%, the through-plane thermal conductivity (TC) and Young's modulus of ISP-PN composites are respectively increased by 163% and 118%, compared to that of the neat PA6 resin. Prevailing over the matrix, the ISP-PN composites own volume electrical resistivity of ~5.11 × 1019 Ω cm. Meanwhile, the TC and mechanical properties of ISP-PN composites are 21.4% and 28.0% higher than the composites obtained by direct melt blending. The improved properties are attributed to the pre-disperse of filler through the masterbatch method. The PA6 chains were immobilized onto the BNNSs-OH by the condensation reaction, resulting in a sort of "chain-extender" and preventing the filler from re-aggregating during the process of melt-blending. This study pioneers a simple and versatile path to melt blending of thermally conductive polymer composites with good mechanical and electrical insulation properties in high-performance thermal management systems. [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]