Submicrometer Sphere Architecture Coated with a Janus Supramolecular Nanolayer ″Garment″: Constructing...

Biologically based polyamide 1012 (PA1012) challenges limitations in fire-sensitive applications due to its inherent flammability, while conventional flame retardants compromise mechanical/dielectric performance. Herein, based on an ingenious micromorphology design, a POSS derivative submicrometer sphere architecture (POSS(Ph-Li)-POM(Mo)@POSS(Ph-Li)) coated with a Janus supramolecular nanolayer was designed to address the critical dilemma of balancing flame retardancy, mechanical integrity, and dielectric performance in PA1012. The Janus architecture conferred dual functionality: lithium-phenyl-decorated POSS strengthened interfacial compatibility with the PA1012 matrix, while polyoxometalate (POM) clusters catalyzed char formation through radical scavenging and carbonization catalysis. In this article, H₃PMo₁₂O₄₀ and Li-Ph-POSS were assembled into a composite flame retardant, POSS(Ph-Li)-POM(Mo)@POSS(Ph-Li), using an electrostatic self-assembly method, and the composite flame retardant was prepared by blending with PA1012. Crucially, incorporating 10 wt % of POSS(Ph-Li)-POM(Mo)@POSS(Ph-Li) into PA1012, the composite retained 91% of its tensile strength (45.15 MPa vs 49.69 MPa), while the dielectric constant decreased to 3.09-2.73 compared with 3.70-3.26 for PA1012. Additionally, thermal analysis revealed an 8.4 wt % increase in residual char yield at 800 °C. Combustion performance tests indicated that the addition of POSS(Ph-Li)-POM(Mo)@POSS(Ph-Li) significantly enhanced the flame retardancy of PA1012, elevating the limiting oxygen index (LOI) from 23.6% to 26.2%. This improvement was attributed to the rapid formation of compact char layers during combustion, which effectively suppressed fire propagation by reducing the peak heat release rate (p-HRR), peak smoke production rate (p-SPR), and peak CO production rate (p-COP) by 39.7%, 35.4%, and 53.3%, respectively. This work developed a paradigm for creatingmultifunctional flame retardants through Janus supramolecular engineering, simultaneously addressing the critical challenges of flammability mitigation and performance preservation in biologically based polyamide.