Conjugated polymers have attracted intense interest for application in photonics, sensing, and light emitting diodes and so on. Among them, poly (3, 4-ethylenedioxythiophene) (PEDOT) have been actively studied due to its excellent electrical and optical properties and its environmental stability. Due to the very poor solubility of PEDOT in water, polystyrene sulfonate (PSS) is introduced to improve its solubility. So, PEDOT:PSS has been used in various applications such as a hole transport layer for solar cells, thermoelectric devices, and transparent electrodes. In addition, PEDOT:PSS can be used as a heat shielding film material because of its high optical adsorption in the near infrared region(NIR).

In order to enhance heat shielding effect of PEDOT:PSS, Park et al(DOI:10.1039/c8ra01122b) adopted two-stage shot growth to prepare Poly(EDOT/Ani):PSS. Firstly, an aqueous dispersion of PSS was bubbled with inert nitrogen gas, 3,4-Ethylenedioxythiophene(EDOT) monomer was added dropwise to the PSS solution with stirring. Then, the oxidizing reagents, sodium persulfate and iron(III) sulfate were added at room temperature. Secondly, aniline (Ani) was added dropwise to the mixture at various time intervals as the second monomer. Finally, residual ions of the mixture were removed and filtered, and liquid solution consisting of PEDOT:PSS and polyAni:PSS was obtained.

Schematic for synthesis of poly(EDOT/Ani):PSS(DOI:10.1039/c8ra01122b)

Poly(EDOT/Ani):PSS was characterized by FT-IR and XPS. The shielding efficiency of the Poly(EDOT/Ani):PSS films was calculated by using data form UV, visible and NIR spectroscopy. The introduction of polyaniline to PEDOT increased the adsorption in NIR. In comparison with PEDOT : PSS film, the total shielding efficiency of the Poly(EDOT/Ani) : PSS film increased to 65.8% from 54.6% at 60% transmittance. The maximum NIR shielding efficiency of the film is 92.7% and the transmittance is 46.5%.

In summary, a conjugated polymer complex with enhanced adsorption in the near infrared area was obtained by controlling time intervals for aniline monomer addition to PEDOT:PSS solution. Poly(EDOT/Ani):PSS shows high heat shielding efficiency in comparing with pristine PEDOT:PSS. And the experimental results show that Poly(EDOT/Ani):PSS can facilitate commercial application of heat shielding film and simplify the preparation of nanocomposites.

Edited by Suzhou Yacoo Science Co., Ltd.