Enhancing the cost-efficiency of hydrogels for thermochromic smart windows through optimization of raw materials and preparation methods

Hydrogels containing polymers with a lower critical solution temperature (LCST) show great potential for thermochromic smart windows due to their excellent optical performances. However, relatively high cost limits their industrial application as building materials. To reduce costs, commodity chemicals acrylamide and diacetone acrylamide were used as raw materials to prepare these hydrogels. Additionally, a composite hydrogel strategy was employed, wherein polyacrylamide hydrogel is combined with a thermosensitive acrylamide/diacetone acrylamide copolymer, further reducing use of the more expensive diacetone acrylamide. Ultimately, by replacing only 3% of acrylamide with diacetone acrylamide, a composite hydrogel with excellent thermal stability and homogeneity during and after clouding was achieved. This hydrogel outperforms two classical systems: hydroxypropyl cellulose solution and poly( N -isopropylacrylamide) hydrogel. Furthermore, the composite hydrogel exhibits excellent luminous transmittance (90%) at low temperature and high modulation capability of luminous transmittance (74%), demonstrating significant cost efficiency for thermochromic smart windows.