Low potential electrosyntheses of free-standing polyfluorene films in boron trifluoride diethyl etherate Jingkun Xu a, * , Yajuan Zhang a,b , Jian Hou a , Zhenhong Wei a,c , Shouzhi Pu a , Jiquan Zhao b , Yukou Du c a Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal University, Nanchang 330013, PR China b School of Chemical Engineering, Hebei University of Technology, Tianjin 300130, PR China c Department of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215006, PR China Received 16 May 2005; received in revised form 25 October 2005; accepted 25 October 2005 Available online 9 December 2005 Abstract High quality free-standing polyfluorene (PFe) films were synthesized electrochemically by direct anodic oxidation of fluorene in pure boron trifluoride diethyl etherate (BFEE) on stainless steel sheet. The oxidation potential of fluorene in this medium was measured to be only 1.1 V versus SCE, which was much lower than that determined in acetoni- trile + 0.1 mol L 1 TBATFB. PFe films obtained from this medium showed good electrochemical behavior, good thermal stability with conductivity of 0.25 S cm 1 , indicating that BFEE is a better medium than acetonitrile for the electrosynthe- ses of PFe films. FTIR and 1 H NMR spectral investigations indicated that the polymerization of fluorene occurred mainly at 2, 7 position. As-formed PFe films can be partly dissolved in acetone, acetonitrile, tetrahydrofuran, etc. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Electrochemical polymerization; Inherently conducting polymers; Polyfluorene; Boron trifluoride diethyl etherate 1. Introduction Among the conducting polymers had been studied during the past quarter century, polyfluorene (PFe) and its derivatives are an important class of electro- active and photoactive materials. In the past seven years, this research field has literally exploded because of PFeÕs exceptional electrooptical proper- ties for applications in polymer light emitting diodes [1–12]. PFe and its derivatives were mainly prepared by two main routes, chemical approaches through Suzuki, Yamamoto and Stille reactions [1,2] and elec- trochemical oxidative polymerization of correspond- ing monomers [13–40]. Because PFe itself was almost insoluble in common organic solvents, the chemical approaches mainly concerned on the alkyl-substi- tuted PFes. Thus the polymer films can be prepared by dip coating or vacuum deposition etc. On the other hand, electrochemical polymeriza- tion had been proved to be one of the most useful approaches for conducting polymer synthesis with several advantages. First, one-step conducting film can be formed on the working electrode. Second, the amount of polymer deposited on the electrode 0014-3057/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2005.10.014 * Corresponding author. Tel.: +86 0791 3805183; fax: +86 0791 3826894. E-mail address: xujingkun@tsinghua.org.cn (J. Xu). European Polymer Journal 42 (2006) 1154–1163 www.elsevier.com/locate/europolj EUROPEAN POLYMER JOURNAL