Chitosan-based bilayer shell phase change nano-capsules with excellent anti-permeability for thermal regulation dressings

Nano-encapsulated phase change materials (NEPCMs) with appropriate phase change temperature range and excellent anti-permeability have significant application value in the field of thermal regulation dressings. In this study, NEPCMs were synthesized using the microemulsion polymerization method, with eutectic fatty acids (LA-SA) as the core material and poly(methyl methacrylate) (PMMA) as the shell material. Subsequently, using the electrostatic adsorption method, chitosan (CS) was successfully coated onto the outer surface of NEPCMs, resulting in the preparation of a novel bilayer shell nano-encapsulated phase change materials (BS-NEPCMs) for thermal regulation dressings. The impact of core/shell ratio, CS acid solution concentration and cross-linking agent content on capsule properties was investigated. It was found that BS-NEPCMs exhibited excellent cyclical stability and thermal stability. In particular, the CS shell layer provided excellent interfacial impermeability effects for the capsules, achieving an anti-permeability efficiency of 96.21 %. This not only helps address the problem of high leakage rates in single wall capsules, but also ensures that the capsules maintain high phase change enthalpies of 99.32 J/g and 96.38 J/g, respectively. The dressings based on BS-NEPCMs demonstrated good thermal regulation at 33–42 °C with maximum phase change enthalpies of 39.53 J/g and 34.08 J/g, respectively. Swelling and rheological analysis showed that the dressing exhibits a gel state, with a swelling ratio of 343 %, an elastic modulus of 15 kPa and a viscous modulus of 4 kPa. This study indicated that BS-NEPCMs hold significant promise for various applications in energy storage and body thermal regulation fields.