Thermo- and pH-responsive starch derivatives for smart window.

A thermo and pH dual-responsive starch (TPDS) was successfully synthesized by etherification, in which butyl glycidyl ether (BGE) was used as the hydrophobic reagent followed by addition of 2-chloro-4, 6-diglycino-[1,3,5]-triazine (CDT) groups. The obtained materials were characterized by Fourier transform-infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1H NMR) and elemental analysis to confirm the structure and the average substitution degree of BGE and CDT on starch molecule. It was observed that the lower critical solution temperature (LCST) of the TPDS could be modulated from 31 °C to 47 °C by increasing pH of the solution. The effects of pH and the concentration of such materials on the energy-saving performance of TPDS which could be potentially used as smart windows were investigated by UV-vis-NIR spectrophotometry. The solar modulating ability (△Tsol) and the luminous transmittance (△Tlum) of the sample were 40.1% and 47.1% when 10 g/L TPDS was chosen at pH 3. The results indicate that TPDS exhibits excellent optical performance with a controllable LCST, which shows great potential for the application as a smart window.