Vol.:(0123456789) 1 3 Journal of Inorganic and Organometallic Polymers and Materials https://doi.org/10.1007/s10904-020-01736-x Fabrication of PMMA‑SiO 2 Transparent Nanocomposite Films as Energy Storage Barriers Y. Dastyar 1  · M. M. Zerafat 1  · A. Jamekhorshid 2 Received: 20 June 2020 / Accepted: 29 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract In the present study, sol–gel synthesized silica shell is selected to encapsulate Na 2 SO 4 ·10H 2 O as the phase change agent with a 30 °C phase change temperature. In the next step, the produced nanocomposites are dispersed in poly (methyl methacrylate) (PMMA) as a transparent polymer to produce flms that can be considered as an alternative for transparent barriers like glass windows. Thermal analysis indicates that the synthesized nanocomposites show an efcient thermal energy storage capacity, which is also preserved through several thermal cycles. Based on the results, the as-prepared phase change material with a 40% encapsulation ratio and 96.29 J/g and 83.03 heating and cooling enthalpies and 32 °C and 10 °C phase change temperatures for heating and cooling, respectively and also no phase separation can be considered as a promising material for inclusion in transparent polymeric matrices as an alternative for glass windows. Keywords Phase change materials · Poly (methyl methacrylate) · Nanocomposite · Sodium sulfate · Thermal energy storage 1 Introduction Considering the extinction of fossil fuels and the force to fnd renewable energy sources, the necessity for energy con- trol and storage is highlighted during recent decades. As a result, utilization of nano-PCMs with high energy adsorp- tion and storage capacity has attracted attention in various applications such as textiles, building materials, defence mechanisms and etc. [1]. Most PCMs perform therml storage through solid–liquid phase change [2] with various melting points in the – 50 to 400 °C range [3, 4] and can be categorized into three groups as eutectic, hydrated salts and inorganic. Hydrated salts are crystalline salt molecules loosely attached to water molecules [5]. Generally, encapsulation of PCMs can be performed in a core–shell structure [6] to prevent toxic or dangerous materials exposure, prevention of moisture loss and also providing shape stability in the liquid state [7]. Among various hydrated salts, hydrated Na 2 SO 4 ·10H 2 O can be considered as a candidate for thermal energy storage with a thermal density of 36.7 × 10 4  kJ/m 3 , which is not the highest. However, availability has proposed Glauber’s salt as a promising candidate for thermal storage [8–10]. The phase change mechanism in hydrated salts is described by hydrated water release and subsequent solution of the base salt in the released water [11]. Thermal energy storage efciency in PCMs is generally enhanced by size reduction to micro and nano scales due to the enhancement of interfacial contact area. As a result, micro/nanoencapsulated PCMs have been synthesized through various techniques, such as emulsion polymeriza- tion, interfacial polymerization and sol–gel [12]. Shells can be polymeric or inorganic for diferent applications, where inorganic shells are advised at high temperature applications or long exposure periods to lower temperatures; thus silica nanocapsules can be a good choice in this regard [13, 14]. Glass windows guide the daylight into buildings but due to high thermal conductivity have adverse efects on energy efciency. Transparent PCM flms are advised as a solution to this problem due to low thermal conductivity [15]. Highly transparent PCMs are viable as an alternative for incorpora- tion into glass or thermoplastic polymers [16]. Transparent plastics like polycarbonates, PMMA or poly (tetrafuroeth- ylene) have several advantages in this regard such as lower * M. M. Zerafat mmzerafat@shirazu.ac.ir 1 Nanochemical Engineering Department, Faculty of Advanced Technologies, Shiraz University, Shiraz, Iran 2 Faculty of Petroleum, Gas and Petrochemical Engineering, Persian Gulf University, 75169 Bushehr, Iran