Shape-stabilization of polyethylene glycol phase change materials with chitin nanofibers for applications in "smart" windows.

Polyethylene glycol (PEG) based shape-stabilized phase change materials (PCMs) were successfully prepared using chitin nanofibers (CNFs). CNFs were isolated from crab shells and, resulted CNFs were several tenth of nanometers in diameter and had lengths ranging from several hundreds of nanometers to few micrometers. Introduction of CNFs in to PEG resulted shape-stabilized composites. Various PEG-CNF composites were fabricated and the resulted materials were encapsulated in to an optical device to obtain temperature dependent transparency. In the optimized formulation, the device remained opaque (∼3.5 %) below the melting point of the PEG-CNF composite and became gradually transparent as the temperature of the device increased ultimately stabilizing at a transmittance value of ∼88 %. CNF phase was seen to have an effect on the thermal properties of the PEG-CNF material. The work introduces a novel strategy for the shape stabilization of liquid-solid phase change materials unlocking potential for new PCM based devices.