The orientation of ultrahigh aspect ratio thermally conductive fillers can construct a heat transfer path to enhance the thermal conductivity of composite materials effectively with low filler loading. Nevertheless, single orientation (vertical or horizontal) limited the application of these materials when there was the need for isotropic heat transferring. Here we report a novel strategy to prepare thermally conductive flexible cycloaliphatic epoxy resin nanocomposites with an oriented three-dimensional staggered interconnected network of vertically aligned h-BN (hexagonal boron nitride) platelets and randomly dispersed CNT-NH2 (aminated carbon nanotubes). In this structure, h-BN platelets coated with magnetic particles could respond to the external magnetic field; however, the CNT-NH2 couldn’t. The obtained composites exhibited both through-plane (0.98 ± 0.037 W/m·K) and in-plane (0.99 ± 0.001 W/m·K) thermal conductivity enhancement at low h-BN loading of 30 wt %, and also presented excellent electrical insulating properties (<1.2 × 10–12 S/cm). In addition, the equal value of thermal conductivity of two directions (in-plane and through-plane) was shown when the content of h-BN was about 26.43 wt % and of CNT-NH2 was 2 wt %, displaying no difference between the thermal conductivity of two directions (in-plane and through-plane). The infrared imaging tests showed the outstanding heat dissipation capability of the composites by capturing the surface temperature variations of a heater with the composites as the heat dissipating material.

Developing multiphase polyurethanes (PUs) with loosely packed domains containing dynamic linkages and appropriately crystallized soft phases composed of polycaprolactone diol (PCL) segments is effective for the trade-off between toughness and self-healing. Here, we proposed a new strategy based on mixed dynamic hard segments to achieve the goal and improve self-healing behavior and mechanical performance. The designed polyurethanes comprise a microphase-separated structure with polycaprolactone diol as soft segments, which are facilitated to store entropy energy under strain. The aromatic disulfides together with aliphatic chain extenders were selected as hard segments to adjust the hierarchical structures, including microphase separation and crystallinity. The reversible hydrogen bonds and disulfide bonds distributed in the polymer network contribute to enhancing stretchability and self-healing performance. In this research, the robust polyurethanes with uniform microphase separation structures and insufficient crystallinity were designed by mixing a dynamic hard domain, which exhibits the potential application in the field of flexible conductors and synthetic muscles; the recovery efficiency at 90 °C is 93.8% and the ultimate stress/strain are 18.7 ± 0.2 MPa/2253 ± 149.2%. This work confirmed that the feasibility of synthetic PUs by changing the mole ratio of dual chain extenders simply, which is also expected to inspire the related fields of engineering, may require polymers with excellent self-healing efficiency and extraordinary robustness simultaneously.

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