Leakage-free porous cellulose-based phase change cryogels for sound and thermal insulation

Leakage-free phase change materials (PCM) are used as passive energy storage systems that thermoregulate indoor environments. In this research, we synthesized highly porous hybrid materials based on non-covalent physical interactions between (poly)ethylene glycol (PEG) and modified cellulose nanofibrils (CNF), namely lignin-containing CNF (LCNF) or acetylated CNF (ACNF). The PEG/CNF hybrid, termed phase change nanohybrids (PCN), were ultra-lightweight (0.022-0.043 g/cm3), mechanically resilient, and displayed a high latent energy storage, up to 204 J/g. The PCN systems (specific heat capacity as high as 2.24 J/g K) were effective in thermal regulating 2.23 degrees C with a 1 mm thickness coverage while maintaining thermal stability. The PCN also demonstrated favorable thermal management under excess solar heating, providing 33.5 degrees C of insulative protection with a 1.5 cm thick system. The PCNs have exceptional acoustic absorbance (100% absorbance for 1600 Hz and 50% at lower frequencies, 500 Hz). Trace metal oxide (TiO2) nanoparticles improved the PCN thermoregulating abilities, revealing desirable opportunities in multi-functional applications. Our biobased PCN is a promising insulation and passive energy storage alternative for thermal protection in smart building, electronic, packaging, energy storage system and aerospace sectors.