Thermochromic PNIPAM/CMC/PEG Smart Window with Enhanced Light Regulation Performance

Color-changing materials make up a category of smart materials capable of exhibiting chromatic transitions in response to environmental stimuli. Certain thermochromic materials exhibit tunable optical transmittance during chromatic transitions, allowing for dynamic modulation of solar radiation in energy-efficient window applications. In this work, we develop a low-cost thermochromic poly( N -isopropylacrylamide)/carboxymethyl cellulose sodium/poly(ethylene glycol) (PCP) composite, achieving excellent light modulation and indoor temperature regulation capabilities. The introduction of CMC and PEG significantly enhanced the uniform dispersion of PNIPAM, thereby endowing the material with a highly efficient transition from transparent to opaque. Meanwhile, the results show that the PNIPAM/CMC/PEG smart window has high luminous modulation (Δ T lum = 99.20%) with approximately 100% luminous transmission ( T lum = 99.29%) at 25 °C and approximately 0% transmission ( T lum = 0.09%) at 35 °C. Additionally, the smart window demonstrated long-term stability in dynamic transparent–opaque transitions and a low transition temperature of 30.9 °C. Therefore, the proposed composite presents several advantages, including high efficiency, low cost, and easy scalability, offering new insights into the design and fabrication of smart windows and other smart materials.