Benzotriazole-based conjugated microporous polymers as efficient flame retardants with better thermal insulation properties

Abstract

The development of high performance flame retardant materials with better thermal insulation properties is of great importance for saving energy in modern building construction. Herein, we report for the first time the synthesis of novel conjugated microporous polymers (CMPs) using monomers containing a benzotriazole moiety as building blocks via Sonogashira–Hagihara cross-coupling polymerization. The synthesized ZCMPs show high thermal stability with a decomposition temperature above 330 °C and high specific surface area up to 691 m² g⁻¹. The resulting CMP samples possess excellent flame retardancy with a peak heat release rate (pHRR) as low as 9.9 W g⁻¹, which is nearly one order of magnitude lower than those of many traditional polymeric flame retardants reported previously. Also, they also show better thermal insulation properties with a thermal conductivity of ca. 0.03 W m⁻¹ K⁻¹ in air. More importantly, the introduction of a benzotriazole moiety into CMPs could generate nitrogen (a “green” gas compared with many flame retardants) to produce a flame-retardant effect. In addition, the rigid porous structure of CMPs could nearly remain to form a carbon layer as a barrier to block oxygen, mass, and heat transfer to the substrate when it undergoes high temperature treatment. Considering the advantages mentioned above, CMPs may hold great potential for future thermal insulation and flame retardant applications.