Synthesis of novel chiral l-leucine grafted PEDOT derivatives with excellent electrochromic performances

Two amino acid-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives, poly(N-(tert-butoxycarbonyl)-l-leucyl(3,4-ethylenedioxythiophene- 2′-yl)methylamide) (PEDOT-Boc-Leu) and poly(l-leucyl(3,4- ethylenedioxythiophene-2′-yl)methylamide) (PEDOT-Leu) were synthesized electrochemically via potentiostatic polymerization of corresponding monomers N-(tert-butoxycarbonyl)l-leucyl(3,4-ethylenedioxythiophene-2′-yl) methylamide (EDOT-Boc-Leu) and l-leucyl(3,4-ethylenedioxythiophene-2′-yl) methylamide (EDOT-Leu), which were synthesized by grafting Boc-l-leucine and l-leucine into a 3,4-ethylenedioxythiophene (EDOT) side chain. The electrochemical behaviors, structural characterization, circular dichroism, spectroscopic properties, surface morphology, electrochromic properties and thermal stabilities of PEDOT-Boc-Leu and PEDOT-Leu films were systematically investigated. These l-leucine grafted PEDOT derivatives displayed excellent reversible redox activities, rough and compact surface, and good thermal stability. The circular dichroism spectra suggested the chirality of these polymers. Importantly, the introduction of the l-leucine group enhanced the electrochromic properties of PEDOT and resulted in high contrast ratios (ΔT% = 49% at 600 nm for PEDOT-Boc-Leu) and high coloration efficiencies (431 cm² C^-1 at 960 nm for PEDOT-Leu). Satisfactory results implied that the obtained polymer films can probably be further developed in various applications, such as electrochromic devices, optical displays and chiral recognition.