Temperature-responsive hydroxypropylcellulose based thermochromic material and its smart window application

Thermochromic materials are the most cost effective smart window materials and the organic hydrogel material has large solar modulating ability (Delta T-sol) and the luminous transmittance (T-lum) compared with inorganic VO2 based materials. Here we report a green and new organic thermochromic material based on hydroxypropylcellulose. With increasing addition of NaCl from 0.5% (wt%) to 5% (wt%), the LCST (lower critical solution temperature) could reduce from 42 degrees C to 30 degrees C. The morphology change of freeze dried samples below and above LCST proves that the phase change of this hydroxypropylcellulose based hydrogel is due to the solubility change of the polymer in water. The fine-tuned recipe can give an outstanding solar modulating ability (Delta T-sol) of 25.7% and high averaged T-lum of 67.4% with LCST of 38 degrees C.