Highly Stable\nComposite Phase-Change Materials Reinforced\nby Silica Aerogels and Cellulose Nanocrystals for Enhanced Thermal\nInsulation and Durable Isoperibolic Application

The reduction in thermal conductivity\nof composite phase-change\nmaterials (PCMs) enhanced with silica aerogels (SAs) is garnering\ninterest across various fields. However, the integration of SAs into\nsubstrates poses a challenge due to their high specific surface area\nand lightweight properties. In this research, we successfully developed\na PCM reinforced with SA and cellulose nanocrystals (CNC) (paraffin\nwax (PW) @CNC/SA @poly(vinyl alcohol) (PVA), PW@CNC/SA@PVA). Here,\nrenewable CNCs function as effective Pickering emulsifiers for encapsulating\nPW, while PVA acts as a binder, stabilizing the SA and maintaining\nits nanoporous integrity. The amphipathic nature of CNCs plays a crucial\nrole in securely encapsulating PW with an impressive content of 63\nwt %. The specific latent heat capacity of PW@CNC/SA@PVA was measured\nto be approximately 106 J/g. Remarkably, this material exhibited minimal\nleakage (about 2 wt %, over 2 h) at temperatures exceeding its melting\npoint (60 °C). Additionally, the uniform dispersion of hydrophobic,\nporous SAs within the PVA solution imparts PW@CNC/SA@PVA with a unique\nblend of low thermal conductivity and ultralight properties. In a\nsimulated scenario resembling sunlight exposure, the designed PW@CNC/SA@PVA\ndemonstrates significant potential for long-term isoperibolic applications.