Totally-organic near-infrared shielding materials by conductive cellulose nanofibers

We synthesized poly(3,4-ethylenedioxythiophene) (PEDOT) thin films by using a microcrystalline sulfated cellulose nanofiber (s-CNF) dopant. Specifically, we examined the ratio of EDOT monomer and CNF dopant, the quantity of initiator for the monomer, and the pH during polymerization. By doing so, we produced a PEDOT/s-CNF thin film with a conductivity that is 700 times higher than commercial simple PEDOT/polystyrene sulfonate (PSS) without adding agent. The optical adsorption of PEDOT/s-CNF thin film in the near-infrared (NIR) range (700-2000 nm) increased in accordance with the electrical conductivity increased. We estimated the visible light (380-700 nm) and NIR (700-2000 nm) transmittance tau by multiplying the spectral transmittance tau(lambda) and weighting coefficients (E-lambda center dot Delta lambda), and taking the weighted average. Although the tau(vis) of the optimized PEDOT/s-CNF thin film with the highest conductivity remained at 85.0%, the tau(NIR) decreased to 69.8%. We dispersed the optimized PEDOT/s-CNF in the polyvinyl alcohol aqueous solution and coated the polymer onto a glass plate to provide NIR shielding. By testing the PEDOT-coated glass by irradiation with simulated sunlight, we confirmed that the film suppressed the temperature rise.