Development of smart window using an hydroxypropyl cellulose-acrylamide hydrogel and evaluation of weathering resistance and heat shielding effect

Reducing the amount of electricity used by cooling systems is essential for lowering CO2 emissions; therefore suppressing increases in room temperature in an environmentally friendly manner requires the development of heat-shielding materials that autonomously control sunlight without the use of electricity. Hydroxypropyl cellulose (HPC) has attracted attention as a lower critical solution temperature (LCST) type of temperatureresponsive polymer. HPC is a thermochromic material that changes its optical properties in response to changes in external temperature. In this study, acrylamide (AAm) and HPC with various molecular weights were used to prepare HPC-AAm hydrogels, and their optical, heat-shielding, and weathering-resistant properties were evaluated. UV-vis-NIR spectroscopy revealed that the solar transmittance (alpha Tsol) of the HPC-AAm hydrogel decreased while its solar reflectance (alpha Rsol) increased with increasing HPC concentration above LCST. The alpha Tsol of low-molecular-weight HPC was found to be lower than that of high-molecular-weight HPC. In addition, the temperature inside a box constructed using an HPC-AAm hydrogel window was approximately 10 degrees C lower than that constructed using glass alone. Furthermore, the optical properties of the HPC-AAm hydrogel were found to hardly deteriorated even when continuously exposed to heat and UV radiation for 150 h. Therefore, the HPCAAm hydrogel prepared in this study is expected to be useful as a heat-shielding material.

Automated summary

The study prepared HPC-AAm hydrogels using HPC and AAm, which showed excellent optical, heat-shielding, and weathering-resistant properties. Above LCST, the solar transmittance of HPC-AAm hydrogels decreased while the solar reflectance increased. Additionally, the use of HPC-AAm hydrogel windows significantly reduced the indoor temperature.