Room-temperature hydrogen bonding and high-temperature rearrangement towards high-performance flame-retardant aliphatic polyamide

With the increasing public awareness of safety and the ongoing global legislation on the use of flame retardants, the development of eco-friendly flame-retardant methods has become an urgent issue. In this study, we utilized the room-temperature hydrogen-bonding effect and the high-temperature rearrangement inherent in the functional hydroxyl-containing phenylimide structure to engineer a flame-retardant, high-performance aliphatic polyamide. Remarkably, the obtained polyamide copolymer was exclusively composed of the elemental constituents inherent to polyamide itself, i.e., carbon, hydrogen, oxygen, and nitrogen. As expected, the high-temperature rearrangement along with the corresponding char-forming and end-group-capturing effect significantly improved the flame retardancy of the copolymer, characterized by an UL-94 V-0 rating with great anti-dripping performance, 41% reduction in peak heat release rate and 50% reduction in total heat release. The room-temperature hydrogen bonding largely mitigated the deterioration of the chain symmetry and regularity caused by the incorporation of the monomer, thus resulting in substantial preservation of mechanical properties. Furthermore, the copolymer exhibited low dielectric properties and high heat resistance, thereby broadening its potential application domains. This work presented a novel flame-retardant-free strategy for achieving both flame retardancy and high performance in polymeric materials, meeting the increasingly stringent demands for environmental protection and safety.