Understanding the colorimetric properties of quinoxaline-based pi-conjugated copolymers by tuning their acceptor strength: a joint theoretical and experimental approach

Abstract

A series of five new p-conjugated donor-acceptor-donor (DAD n ) copolymers are presented, combining a common donating unit (substituted propylenedioxythiophene, ProDOT-(OEtHx)) with five diphenylquinoxaline based acceptor units bearing substituents of increasing acceptor strength (OMe < H < F < COOMe < CN). The DAD n copolymers, namely P3-X (X ¼ OMe, H, F, COOMe, CN), have been studied in solid state by cyclic voltammetry to investigate their electronic properties during n-and p-doping processes and to determine their electrochemical band gap. UV-Vis spectroscopy reveals a dual-band absorption system in which both high energy and low energy band (HEB and LEB) positions and intensities are governed by the acceptor strength. Density functional theory (DFT) computations were performed on D-A-D trimer model compounds in order to understand the experimental results. A colorimetric study in the CIELAB color space revealed that the modulation of the acceptor strength with s-or p-electron withdrawing/donating groups leads to shades of blue to green upon increasing the acceptor strength. The polymers can also switch to a grey color upon p-doping. Finally, a detailed discussion on color-structure relationship provides valuable insights on molecular design principles to render cyan and green colors.

An Electrochromic Displays Comprising The Three Primary Cyan Magenta and Yellow Colors Under Juxtaposed and Stacked Architectures

“…Compared to the ideal dyes, it mainly indicates the lower saturation and brightness of the rendered colors of devices (C*) while the hue is satisfying as attested by the h value. While it is quite easy to find in the literature ECP reproducing the yellow and magenta colors, the cyan color is very difficult to obtain with Donor‐Acceptor polymers, as we demonstrated formerly, [ 31 ] Modifying the nature of the acceptor unit in the polymer (i.e., its accepting strength and its steric effects) result in severe evolution of a* and b* coordinates, hence the color shifts from a color close to cyan toward the blue or to the green zone. Among all tested Donor‐Acceptor polymers, benzothiadiazole acceptor unit was the best compromise for Cyan.…”

Synthetic Methodologies for Chelating Polymer Ligands: Recent Advances and Future Development

“…A number of π‐conjugated donor‐acceptor‐donor copolymers are obtained to combine the common donor unit (substituted propylene dioxythiophene) with diphenylquinoxaline‐based acceptor units bearing substituents with increasing acceptor force (OMe < H < F < COOMe < CN) (Scheme ) …”

The Availability of Neutral Cyan, Green, Blue and Purple Colors from Simple D–A Type Polymers with Commercially Available Thiophene Derivatives as the Donor Units

“…The band gaps of donor–acceptor (D–A) type polymers could be fine-tuned through the reasonable combination of the donor unit and the acceptor unit, which can be implemented by two possible approaches. The first approach lies in the modification of the molecular structure of the donor unit or the alteration in the number of donor units incorporated in the polymer backbone [ 13 , 14 ]. Similarly, the second approach is characterized by the modification on the acceptor unit, as reported extensively.…”

“…Similarly, the second approach is characterized by the modification on the acceptor unit, as reported extensively. The donor units used usually consist of thiophene and its derivatives, including thiophene [ 3 ], diakoxythiophene (DalkOTs) [ 15 ], propylenedioxythiophene (PPETh) [ 13 ], thieno[3,2-b]thiophene [ 16 ], and benzodithiophene, etc. [ 17 ].…”