Chitosan aerogel composites with durable flame retardancy and prominent water resistance by one-step blending method

Traditional chitosan (CS)-based aerogels suffer from inherent flammability and hygroscopicity, leading to structural collapse and property degradation upon water exposure, which severely limits their practical application. To address these challenges, a kind of copolymer emulsion (CPE) integrated with flame-retardant phosphorus groups and hydrophobic fluorinated groups was developed, and was applied directly to the preparation of CS-based aerogels through simply one-step method. Based on low-surface-energy properties of fluorinated groups aggregated to the surface and physical interaction force of both hydrogen bond and electrostatic interaction between CS and CPE, CS/CPE 0.20 with 20 wt% of copolymer content (F content is lower than 5%) demonstrates great flame retardancy (V-0, LOI = 37.5%), superior hydrophobicity (WCA = 134.1°) and enhanced mechanical properties (compressive strength increased by 200% in radical direction). Significantly, by synergistic effect of hydrophobic protection and structure stability, the dimensional and performance stability of CS/CPE 0.20 on structure, flame retardancy and hydrophobicity still exhibit excellently even after 48 h at 75% relative humidity. Meanwhile, CS/CPE 0.20 also has well oil-water separation performance, solvent adsorption, wet stability and antifouling properties. Consequently, by this simple blending in preparation process, CS-based aerogel composite could achieve multi-functions especially durable flame retardancy and prominent water resistance, which would be effectively used in many practical applications. Compared to traditional functional-modification methods by multi-steps that may be not that stable and uniform, this integrated CPE by one-step strategy not only displays more stable multi-functions but also ensures durable flame retardancy and water resistance through strong interfacial interactions.