Abstract Vanadium dioxide (VO2)–based thermochromic films are of great interest for energy-saving smart windows as they can dynamically change the solar transmittance as the ambient temperature changes. However, VO2 is thermodynamically unstable and could be easily oxidized by the oxygen and moisture in the ambient air. In this work, a durability-enhanced VO2 nanoparticle-polymer thermochromic film was proposed and fabricated using the blade coating method where the cross-linked and highly entangled poly(methyl methacrylate) (PMMA) chains with a molecular weight (~ 950,000) was adopted to block gas diffusion in the polymer matrix. It was shown that the developed VO2 nanoparticle film kept ~30% of its solar modulation ability after ~900 h of accelerated durability test in the aging environment with a temperature at 60 °C and ~95% relative humidity. This is ~4 times of the lifetime of the VO2 nanoparticles which are embedded in the non–cross-linked PMMA matrix with low molecular weight (~15,000). The cross-linked PMMA-VO2 film also showed a high luminous transmittance of ~50%, a high solar modulation ability of ~17%, and a low haze of ~11%. Our method provides an easy and effective strategy to improve the lifetime of VO2 nanoparticles, showing a promising pathway toward environmentally stable and easily scalable thermochromic films for energy-efficient smart windows.

中文翻译：

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用于智能窗户的耐久性增强型二氧化钒热致变色膜

摘要 基于二氧化钒 (VO2) 的热致变色薄膜可以随着环境温度的变化动态改变太阳光透射率，因此在节能智能窗户方面具有重要意义。然而，VO2 在热力学上不稳定，很容易被周围空气中的氧气和水分氧化。在这项工作中，提出了一种耐久性增强的 VO2 纳米颗粒聚合物热致变色膜，并使用刮刀涂布法制造，其中采用了分子量为（~950,000）的交联和高度缠结的聚（甲基丙烯酸甲酯）（PMMA）链阻止气体在聚合物基质中的扩散。结果表明，在温度为 60°C 和相对湿度约 95% 的老化环境中，经过约 900 小时的加速耐久性测试后，开发的 VO2 纳米粒子薄膜保持了约 30% 的太阳能调制能力。这是嵌入低分子量 (~15,000) 的非交联 PMMA 基质中的 VO2 纳米粒子寿命的约 4 倍。交联的 PMMA-VO2 薄膜还显示出~50% 的高透光率、~17% 的高太阳能调制能力和~11% 的低雾度。我们的方法提供了一种简单有效的策略来提高 VO2 纳米粒子的寿命，显示出一条通往环境稳定且易于扩展的热致变色薄膜的有前途的途径，用于节能智能窗户。