Synthesis and chemical properties of electrochromic π‐conjugated polyphenylenes with pendant viologen‐TCNQ salts

Abstract

AbstractPolyphenylene (PP) with NH2 side groups, namely, PFluNH2, was synthesized by the Pd‐catalyzed reaction of 2,5‐dibromoaniline with 9,9‐dihexylfluorene‐2,7‐diboronic acid bis(1,3‐propanediol) ester. The reaction of PFluNH2 with 1‐hexyl‐1′‐(2,4‐dinitrophenyl)‐4,4′‐bipyridinium diiodide (SaltBPy(I−)) eliminated 2,4‐dinitroaniline to yield PPs with viologen (1,1′‐disubstituted 4,4′‐bipyridinium dications), PFluBPy(I−). The reaction of PFluBPy(I−) with Li+TCNQ− resulted in anion exchange between Cl− and TCNQ−, and yielded PFluBPy(TCNQ−). The reaction of PFluBPy(TCNQ−) with the neutral TCNQ0 resulted in an interaction between TCNQ− and TCNQ0, and yielded PFluBPy(TCNQ−‐TCNQ0). Cyclic voltammetry measurements suggested that an electrochemical reduction of the viologen moiety and oxidation of the polymer backbone within PFluBPy(TCNQ−) and PFluBPy(TCNQ−‐TCNQ0). Furthermore, this reaction was accompanied by electrochromism. The electric conductivities (σ) of the pellets molded from PFluBPy(TCNQ−) to PFluBPy(TCNQ−‐TCNQ0) were 2.7 × 10−4 and 4.2 × 10−4 Scm−1, respectively; these σ values were higher than that observed for PFluNH2 (σ < 10−8 Scm−1) due to the self‐doping in the polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013