Electrical Chiral Assembly Switching of Soluble Conjugated Polymers from Propylenedioxythiophene-Phenylene Copolymers

Abstract

A π-conjugated polymer of propylenedioxythiophene-phenylene (ProDOT-Ph) with a chiral alkyl substituent on the propylene bridge of ProDOT was prepared to explore reversible multiswitching chiral conjugated polymers (CCPs) capable of electrochromic, electrofluorochromic, and chirality switching. The chiral assembly of the yellow colored poly(ProDOT-Ph)s (YPCr) was optimized by annealing the YPCr films at 120 °C. From the thermally annealed YPCr films, we demonstrated the electrical switching of chirality, color, and fluorescence in a single device, for the first time, which was precisely controlled electrochemically to achieve highly efficient and reversible switching of chiral assembly at a low working potential. The YPCr films showed electrochromism with a high coloration efficiency of 690 cm 2 C −1 by changing color between yellow and blue. The film also exhibited fluorescence switching with a quantum yield change from 3.8 to 0.21 during the reversible electrochemical switching. The chirality of the YPCr, which showed a negative bisignate Cotton effect, was switched reversibly with 97% change in the anisotropy factor (g abs ). The multiswitching properties were correlated to the electrochemical switching in chiral assembly of conjugated polymers according to the electrochemical doping/dedoping process. To the best of our knowledge, the change in Cotton effect during the switching is the highest reported value of a chirality tunable polymer without any chiral inducer. In addition, the YPCr showed a sustainable memory effect for both chirality and coloration.

Recent Progress on Circularly Polarized Luminescent Materials for Organic Optoelectronic Devices

“…When increasing the duration of the pulses, the g EL exhibited a gradual enhancement with a slight bathochromic‐shift in EL spectrum. Similarly, dioxythiophene–phenylene copolymer ( 214 ) with a chiral alkyl substituent has been prepared and showed the self‐assembly through thermal annealing . The thermally annealed 214 films exhibited the reversible fluorescent electrochromism between yellow and blue color with the change of luminescent efficiency from 3.8% to 0.21%.…”

“…There are many factors which affect the g lum , such as temperature, ions, force, concentration, solvent polarity, orientation, etc. For example, Kim and co‐workers synthesized a π‐conjugated polymer, the CPL signals of which are not only inversely proportional to its molar concentration in chloroform–methanol solution, but also closely related to the thickness of film and the intensity of applied voltage . Guimarães and co‐workers developed a kind of small molecules with chiral units for self‐assembly, and the magnitude of g lum factors and the intensity of left‐ and right‐circularly polarization increased with the decrease of temperature .…”

Electroluminochromic Materials and Devices

“…Notably, Audebert et al presented such an overview article on EFC related small molecular materials and characterization techniques . However, the past 3 years have seen increasing research reports on ELC materials, especially polymers . More recently, several high‐performance ELC devices that were made by versatile methods exhibited multicolor emissions switching, fast response rate, high luminescence contrast and long‐term stability .…”

Electroswitchable optical device enabling both luminescence and coloration control consisted of fluoran dye and 1,4-benzoquinone

“…Among these multifunctional materials, electrical stimuliresponsive molecules are particularly suitable for display applications because the electrical stimuli can be applied rapidly and reversibly [39][40][41][42][43][44][45]. Because of these advantages, electrical stimuli have attracted much attention.…”