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据悉， 美国麻省理工学院(MIT)研发出一种可以贴在窗户上的智能薄膜，在夏天可以阻隔70%的阳光热量，从而降低室温，可以减少10%的空调电费。MIT研究人员使用polyNIPAm-AEMA共聚物微粒材料制作出常温下透明，但是在夏天较高温度下变白的材料。当暴露在32℃ (89℉)或更高的温度下，这种薄膜会收缩并变得不透明，原理是薄膜内部的polyNIPAm-AEMA共聚物颗粒材料的尺寸在临界温度前后发生突变，温度高于临界温度时（LCST：32℃ ），由1388nm粒径收缩变成546nm粒径，与可见光波长类似，光散射导致材料变成不透明，这种临界变化现象，对于研究过polyNiPAM的童鞋来说再熟悉不过了。而在32℃以下，薄膜则是高透明的，由于此时polyNIPAm-AEMA共聚物颗粒微粒子的尺寸大于可见光波长，低光散射使材料保持高透光率，材料的这种特性，如果用于窗户，在夏天可以阻隔70%以上的阳光热量，可以显著节省空调能耗。

图示：当温度低于polyNIPAm-AEMA的临界温度（LCST）时候（上图第一部分），材料保持透明，当手与薄膜材料接触后，材料温度逐渐上升，高于材料的临界温度时，polyNIPAm-AEMA收缩，使薄膜变成不够透明（上图第二部分）。

参考文献：Broadband Light Management with Thermochromic Hydrogel Microparticles for Smart Windows

Control of solar transmission through windows promises to reduce building energy consumption. However, the ability of current chromogenic technologies to regulate solar gain with the tunable extinction of phase-change materials is still far from optimum. We report a strategy for optimizing the transmittance modulation range of temperature-responsive hydrogel particles by means of tuning the light-scattering behaviors through controlling particle size and internal structure. An emerging thermochromic material, poly(N-isopropylacrylamide)-2-aminoethylmethacrylate hydrochloride (pNIPAm-AEMA) microparticles, was synthesized to demonstrate this strategy. The average size of pNIPAm-AEMA microparticles varies from 1,388 nm at 25°C to 546 nm at 35°C, contributing to an unprecedented infrared transmittance modulation of 75.6%. A high luminous transmittance of 87.2% at 25°C had also been accomplished. An investigation of the tunable scattering behaviors of pNIPAm-AEMA particles provided mechanistic insight into light management by this class of materials, the application field of which is beyond energy-saving smart windows.