290520 Preparation and Characterization of Thermochromic VO2/PNIPA Nanocomposite Hydrogels

Monday, October 29, 2012
Hall B (Convention Center )
Jingxing Feng, School of Chemical Engineering, East China University of Science and Technology, Shanghai, China, Mi Wang, School of Chemical Engineering, East China University of Science and Technology, Xuhong Guo, School of Chemical Engineering, East China University of Science and Technology, Shanghai, China and Yanfeng Gao, Shanghai Institute of Ceramics , Chinese Academy of Sciences, Shanghai, China

Hypovanadic oxide (VO2) has attracted much attention as a thermochromic material for smart windows due to its ability to modulate the near-infrared radiation. VO2 coating can transmit the near-infrared irradiation in cold weather and block most of it in hot weather while maintaining visible transmittance. Poly(N-isopropylacrylamide) (PNIPA) hydrogel is the first reported non-ionic material exhibiting a temperature dependent phase transition which can change from a transparent state at low temperature to a turbid state at high temperature. In this paper, VO2/PNIPA nanocomposite hydrogels with different VO2 contents were prepared by in-situ polymerization. VO2 nanoparticles (~ 50 nm) with the light regulation capability of about 14% in the wavelength range from 350 to 1350 nm were synthesized by a hydrothermal method. As the light-control ability of PNIPA varies with cross-linking density, N,N’-methylenebisacrylamide was used as a crosslinker and the visible transmittance value is more than 50% at 25 °C and less than 10% at 80 °C. VO2 with the amount of 0.5, 1 and 2 wt% of NIPA were added and dispersed in water before polymerization. Results show that VO2 has no impact on the lower critical solution temperature (LCST) of the PNIPA hydrogel. With increasing VO2 content, the viscosity of hydrogel increased, which implied that VO2 probably played a role as crosslinker as well as filler in the reaction. The obtained smart coating showed excellent stability and satisfactory light modulation efficiency.

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