(256g) The Structure and Phase Change Behavior of the Nanostructured Polyethylene Glycol/Silica Hybrid Material

Phase change materials (PCMs) are functional materials with thermal energy storing ability, and can be applied in many fields such as in solar energy storage, waste heat recovery, electric appliances with thermostatic regulators, temperature-adaptable greenhouses, and so on. Among present phase change materials, organic-inorganic hybrid as form-stabilized solid-liquid phase change materials have significant advantages, and are being paid increasing attention. Polyethylene glycol (PEG) is a kind of linear polymer with wide range of melting temperature and larger latent heat, and is a potential PCM for many applications. To be a form-stabilized PCM, PEG is confined in the nanoscale pores or network of a support matrix. Depending on the microstructure of the form-stabilized PCM, the phase change behavior of PEG in such nanostructured hybrid material is different from the free PEG. To study the structure and phase change behavior of nanostructured PEG/SiO2 hybrid, we prepared PEG/SiO2 hybrid as the form-stabilized PCM by sol-gel procedure using Na2SiO3 as silica source. The microstructure of the prepared hybrid material was observed by canning electron microscope (SEM) and transmission electron microscope (TEM). The phase change behavior of PEG in the silica networks was investigated by differential scanning calorimeter (DSC). The SEM and TEM results showed that the prepared material was a nanostructured hybrid of PEG and SiO2, and PEG in network of SiO2 was a small agglomerate with an average size scale ~100 nm. The DSC results showed that the melting heat of PEG in PEG/SiO2 hybrid networks reduced with increase of SiO2 content. No melting heat was detected when the PEG content was lower than 50wt% in the hybrid material. The melting point of PEG confined in the hybrid network was lower than that of the free PEG.