Electrochemical Preparation Of Polyfluorene And Its Derivative From Boron Trifluoride Diethyl Etherate And Performances Investigation

Electrochemical oxidation is an important method for preparing conductivepolymers, and it is featured by fast preparation and facile operation that enable thetechnique to promote and broaden the application of conductive polymers as a newclass of materials. However, the approach to improve the optical and electrochemicalperformances of conductive polymers has become one of the targets in the relatedsociety. Among those aromatic compounds, polyfluorene （PF） and its derivatives withdifferent substituents on the C-9position serving as a class of fluorescent organics,have been used as primary materials in optoelectronic field. In this paper,electrochemical preparation of PF in boron trifluoride diethyl etherate （BFEE） andelectrochemical characterization were introduced, and composite electrode based onactivated carbon （AC） and PF were fabricated and examined. Based on theseinvestigations,9,9-bis （3,6,9-trioxadectyl）-fluorene （BTODF） was successfullyobtained via organic synthesis as well as electrochemical polymerization intocorresponding polymer. By this method, uniform poly [9,9-bis （3,6,9-trioxadectyl）-fluorene]（BTOD-PF） film with electroactivity was prepared, on thisbasis, optical and electrochemical investigation were carried out. The primaryexperimental and conclusion are given as follows:1. Electrochemical preparation of PF film in BFEEUniform PF film with no ketonic site was prepared in BFEE by containingtrifluoroacetic acid（TFA） in different volumes. The lowest oxidation onset potential offluorene in BFEE with50%TFA by volume was measured as0.91V vs Ag/AgCl,much lower than that in acetonitrile （ACN）. According to spectral analysis, the PF is a 1,2,4tri-substituted polymer with the bonding manner of2and7positions, and theaverage degree of polymerization calculated from infrared absorption spectra is10that had PF a higher conjugated length. Moreover, the obtained PF is a good blue lightemitting material and is not soluble in polar solvents such as THF, DMSO, CHCl3. Inaddition, the PF obtained from BFEE-TFA mixed electrolyte exhibits a reversibleredox property in1M LiClO₄/ACN electrolyte, and new opportunities of the PF canbe thus provided for the application in electrochemical capacitor.2. The fabrication of AC/PF composite electrode via electrochemical methodAC electrode was fabricated on stainless steel net as the collector and exhibitedcharacteristic double layer electrical capacitance. The AC electrode waselectrochemically modified by PF to form the composite electrode in the BFEE-TFAmixed electrolyte. The trial of organic fluorescent material as electrodeposited on ACelectrode was made. As followed, cyclic voltammetry and galvanostaticcharge-discharge examinations of the composite electrode were performed in1MLiClO₄/ACN electrolyte, and the specific capacitance can reach227.1F g^-1contributed by double layer electrical capacitance and non-faradic capacitance. Thecyclability of the composite electrode was also performed by galvanostaticcharge-discharge for1200times at the current density of3mA cm^-2, the columbicefficiency kept over95%and the remained specific capacitance was around78%, thestability and characteristic electrochemical capacitance can be thus shown. The ESRof the composite electrode calculated from the galvanostatic discharge curve waslarger than the AC electrode, indicating electrical resistance of the modified PF layer.3. Synthesis of fluorene derivative and its anodic oxidative polymerizationThe C-9position of fluorene was chemically modified by3,6,9-trioxadectylgroups and the derivative9,9-bis （3,6,9-trioxadectyl）-fluorene was successfullyobtained. The products was separated and purified, to satisfy the characterization ofFourier Transform Infrared absorption （FTIR） and Ultraviolet absorption spectroscopy（UV-vis） as well as1H NMR to ensure the monomer as designed. The purifiedBTODF monomer was dissolved in BFEE for potentiodynamically oxidativepolymerization, and a green polymer film in doped state was prepared. The polymer film appeared yellow in dedoped state. According to the examination of the polymerfilm in BFEE, a good electrochemical redox property was exhibited and the onsetoxidation potential was measured as1.08V vs Ag/AgCl. However, the oxidativepolymerization of BTODF in neutral medium such as ACN did not afford thecorresponding polymer. The polymer film obtained from BFEE was characterized byFTIR, UV-vis spectroscopy and photoluminescent spectroscopy, and no ketonic sitewas found, indicating the stability of the side chains after oxidative polymerization.