Chen Fuping, Wu Xuewei, Lu Guoqiang, Nie Jun, Zhu Xiaoqun
State Key Laboratory of Chemical Resource Engineering, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China.
ACS Appl Mater Interfaces. 2024 Apr 9. doi: 10.1021/acsami.3c19272.
With the fast economic development and accelerating urbanization, more and more skyscrapers made entirely of concrete and glass are being constructed. To keep a comfortable indoor environment, massive energy for air conditioning or heating appliances is consumed. A huge amount of heat (>30%) is gained or released through glass windows. Using smart windows with the capability to modulate light is an effective way to reduce building energy consumption. Thermochromic hydrogel is one of the potential smart window materials due to its excellent thermal response, high radiation-blocking efficiency, cost-effectiveness, biocompatibility, and good uniformity. In this work, polyhydroxypropyl acrylate (PHPA) hydrogels with controllable lower critical solution temperature (LCST) were prepared by photopolymerization. The transition temperature and transition rate under "static transition" conditions were investigated. Unlike "static" conditions in which the transition temperature was not affected by the initial and final temperature and heating/cooling ramp, the transition temperature varied with the rate of temperature change under dynamic conditions. The "dynamic" transition temperature of the PHPA hydrogel gradually increased with the increase of the heating rate. It was the result of the movement of the molecular chains lagging behind the temperature change when the temperature change was too fast. The results of the solar irradiation experiment by filling PHPA hydrogels into double glazing windows showed that the indoor temperature was about 15 °C lower than that of ordinary glass windows, indicating that it can significantly reduce the energy consumption of air conditioning. In addition, a wide range of adjustable transition temperatures and fast optical response make PHPA hydrogels potentially applicable to smart windows.
随着经济的快速发展和城市化进程的加速，越来越多完全由混凝土和玻璃构成的摩天大楼正在兴建。为了保持舒适的室内环境，空调或供暖设备消耗了大量能源。大量的热量（超过30%）通过玻璃窗获得或释放。使用具有光调制能力的智能窗是降低建筑能耗的有效途径。热致变色水凝胶因其优异的热响应、高辐射阻挡效率、成本效益、生物相容性和良好的均匀性，是潜在的智能窗材料之一。在这项工作中，通过光聚合制备了具有可控低临界溶液温度（LCST）的聚丙烯酸羟丙酯（PHPA）水凝胶。研究了“静态转变”条件下的转变温度和转变速率。与“静态”条件下转变温度不受初始和最终温度以及加热/冷却速率影响不同，在动态条件下转变温度随温度变化速率而变化。PHPA水凝胶的“动态”转变温度随着加热速率的增加而逐渐升高。这是温度变化过快时分子链运动滞后于温度变化导致的结果。将PHPA水凝胶填充到双层玻璃窗中进行太阳辐射实验的结果表明，室内温度比普通玻璃窗低约15℃，这表明它可以显著降低空调的能耗。此外，宽范围的可调转变温度和快速的光学响应使PHPA水凝胶具有应用于智能窗的潜力。
