ConspectusPolymer-based commercial products have been manufactured globally at annual scales of hundreds of millions of tons, occupying an important position in people’s daily life and industrial progress, attributed to their light weight, workability, and excellent properties. However, due to their organic composition, polymer materials are sensitive to high temperatures and are easily ignited, frequently leading to serious fire accidents. To address this huge challenge, nano flame retardants with high efficiency and multifunctionality have been regarded as an available approach. First, nano flame retardants significantly increase the melt strength of polymer materials by their extremely large specific surface area and strong interfacial interactions. Second, based on a well-dispersed state, nano flame retardants, especially with layered structures, establish a labyrinth effect to suppress the convective delivery of heat and pyrolysis products. Third, metal-based nano flame retardants chelate with the lone-pair electrons of polymer chains to form a transitional ring structure, thus decreasing the energy barrier to promote the carbonization process. Attracted by these advantages, a large amount of research work has already been dedicated to developing nano flame retardants for enhancing the fire safety of polymer materials.Herein, this Account not only introduces the early discoveries of nano flame retardants but also provides a comprehensive overview of our recent advances in the development of nano flame retardants, the exploration of mechanisms, and applications in emerging frontiers. We first illustrate the initial discovery of nano flame retardants by demonstrating the fundamental mechanisms, synergistic effect with traditional flame retardants, and essential issues in nanocomposite manufacturing. In order to solve the low efficiency of nanomaterials added individually, our research attempts to design nanostructured architectures that integrate multiple nanomaterials with specific mechanisms to produce synergistic effects under complex combustion conditions, thereby further enhancing the flame retardancy efficiency. To enhance sustainability and reduce complex experimental efforts, our research adopts biobased resources and machine learning approaches, respectively, to design novel nano flame retardants. Within the in-depth condensed-phase mechanism, we propose multiple strategies, including the catalytic effect of transition metals and the interfacial charring strategy, which preferentially promote the conversion of pyrolysis products into char layers rather than smoke particles. Building on the intrinsic properties of nanomaterials, our studies further expand the application of nano flame retardants into emerging frontiers such as energy storage, thermal management, and electromagnetic interference shielding, thereby shifting the research perspective from traditional polymer systems toward real-world functional applications. Finally, we outline the future design direction of nano flame retardants, concentrating on artificial intelligence and sustainability, and propose the critical challenges in their practical application.
Cai et al. (Tue,) studied this question.