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據悉， 美國麻省理工學院(MIT)研發出一種可以貼在窗戶上的智能薄膜，在夏天可以阻隔70%的陽光熱量，從而降低室溫，可以減少10%的空調電費。MIT研究人員使用polyNIPAm-AEMA共聚物微粒材料制作出常溫下透明，但是在夏天較高溫度下變白的材料。當暴露在32℃ (89℉)或更高的溫度下，這種薄膜會收縮并變得不透明，原理是薄膜內部的polyNIPAm-AEMA共聚物顆粒材料的尺寸在臨界溫度前后發生突變，溫度高于臨界溫度時（LCST：32℃ ），由1388nm粒徑收縮變成546nm粒徑，與可見光波長類似，光散射導致材料變成不透明，這種臨界變化現象，對于研究過polyNiPAM的童鞋來說再熟悉不過了。而在32℃以下，薄膜則是高透明的，由于此時polyNIPAm-AEMA共聚物顆粒微粒子的尺寸大于可見光波長，低光散射使材料保持高透光率，材料的這種特性，如果用于窗戶，在夏天可以阻隔70%以上的陽光熱量，可以顯著節省空調能耗。

圖示：當溫度低于polyNIPAm-AEMA的臨界溫度（LCST）時候（上圖第一部分），材料保持透明，當手與薄膜材料接觸后，材料溫度逐漸上升，高于材料的臨界溫度時，polyNIPAm-AEMA收縮，使薄膜變成不夠透明（上圖第二部分）。

參考文獻：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.