High‐Quality Electrochromic Polythiophenes via BF₃·Et₂O Electropolymerization

Abstract

Electrochemical polymerization in the strong Lewis acid, boron trifluoride ethylether (BFEE), has been used to prepare electrochromic polythiophene (PTh) and its derivatives: poly(3‐methylthiophene) (PMeTh), poly(3‐bromothiophene) (PBrTh), and poly(3,4‐dibromothiophene) (PDBrTh). The polymerization processes and properties of the resultant films are compared, where possible, to those carried out in traditional organic electrochemical solvents. The polymerization of these high oxidation potential thiophene monomers in BFEE yielded good‐quality, homogenous, and smooth electroactive and electrochromic films that could be repeatedly switched in common electrochemical solvents up to 240, 1380, 560, and 420 cycles for PTh, PMeTh, PBrTh, and PDBrTh, respectively, for 50 % retention of electroactivity. A colorimetric study of these films showed distinctive color changes between red and blue as they were switched between reduced and oxidized states. These findings allow the use of commercially available high oxidation potential thiophene monomers to provide electrochromic polymers, avoiding the use of other custom‐synthesized monomers.

A novel polyfluorene derivative electrodeposited by direct anodic oxidation of 9-bromofluorene in boron trifluoride diethyl etherate and trifluoroacetic acid

“…It is known that BFEE exists in EE as a polar molecule, ½ðC 2 H 5 Þ 3 O þ BF À 4 , and the existence of a small amount of water complexes BF 3 into H + [BF 3 OH] À , which furnishes a conducting medium and leads to mild acidity. Alkan et al [46] speculated that it was the [BF 3 OH] À ion that served as the dopant during the electrochemical polymerization. This result was also can be found in the electropolymerization of indole-5-carboxylic acid in BFEE [26].…”

Electrosyntheses of high quality freestanding polyselenophene films in boron trifluoride diethyl etherate

“…It is well known that freestanding films of polythiophene [11][12][13] and its derivatives [98][99][100][101][102][103][104][105], such as poly (3-methylthiophene) [86,98,99], poly(3-octylthiophene) [100,101], poly(3-bromothiophene) [102], poly(bithiophene) [103,104], poly(terthiophene) [105] and poly(3,4-dibromothiophene) [84], can be easily produced by direct anodic oxidation of corresponding monomers in BFEE with good mechanical, electrical, electrochemical and thermal properties. In this medium, the oxidation onsets of these monomers were much lowered than that in acetonitrile containing small inorganic anions, such as BF À 4 ; ClO À 4 ; PF À 6 , etc..…”

Enhancing the performance of poly(3-methylthiophene)-based electrochromic devices via insertion of a TiO2 buffer layer

“…Doping time was significantly reduced at an applied potential over long periods (2000 cycles); whereas the optical contrast declined to 10%, indicating that long-term operating stability must be improved. Ionic electrolytes of boron trifluoride diethyl ether (boron trifluoride ethylether, BFEE) have been used in all kinds of electrochromic thin films produced with polythiophene derivatives [8], and the optical contrast of these single-layer electrochromic films have the highest value of DT = 46%. In [9], poly-(3,4-ethylenedioxythiophene) was coupled with P3MT in a dual-layer device, in which the ionic electrolyte TBABF4 (tetra-butyl ammonium fluoroborate) was used as an electrolyte.…”