Control of Phase Transition Temperature of Poly(N-isopropylacrylamide) Based Polymers for Thermotropic Smart Window by Copolymerization with Hydrophilic/Hydrophobic Comonomers

Smart windows fabricated with thermotropic polymers can adaptively control the transmittance of the sunlight that enters the room, thereby reducing energy consumption for air conditioning. However, it is difficult to apply to various climatic environments for thermotropic smart windows based in poly(N-isopropylacryamide) (PNIPAm) due to the fixed transition temperature of 32 C degrees In this study, the transition temperature of PNIPAm based polymers could be controlled by copolymerization with the hydrophobic N,N'-diethylacrylamide or the hydrophilic N-vinylpyrrolidone comonomers. We found that the transition temperature shifts to lower or higher temperatures ranging from 24-48 degrees C depending on the composition of copolymers through the controlof the interaction between copolymer and water. We further fabricated the smart window with prepared copolymers and confirmed that the optical transition of the windows occurs at various temperatures.