Electrochimica Acta 69 (2012) 134–138 Contents lists available at SciVerse ScienceDirect Electrochimica Acta j ourna l ho me pag e: www.elsevier.com/locate/electacta Effect of regioregularity on specific capacitance of poly(3-hexylthiophene) P. Sivaraman a,b , Sarada P. Mishra a , Arup R. Bhattacharrya b , Avinash Thakur a , K. Shashidhara a , Asit B. Samui a,∗ a Naval Materials Research Laboratory, Shil Badlapur Road, Anand Nagar, Ambernth-421 506, Thane, Maharashtra, India b Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology, Mumbai 400 072, India a r t i c l e i n f o Article history: Received 21 October 2011 Received in revised form 23 February 2012 Accepted 23 February 2012 Available online 3 March 2012 Keywords: Poly(3-hexylthiophene) Regioregularity Specific capacitance a b s t r a c t In this communication, we investigate the effect regioregularity of poly(3-hexylthiophene) (P3HT) on the specific capacitance. P3HTs with regioregularities 96, 70 and 58% have been synthesized by Grig- nard metathesis (GRIM) and FeCl 3 methods. The regioregularity of P3HTs are characterized by nuclear magnetic resonance (NMR), UV–Vis spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. Electrochemical characterizations of the P3HTs reveal significant increase in the specific capacitance with increase in regioregularity. Electrochemical impedance spectroscopy analysis indicates that the charging process is facilitated by increase in regioregularity in P3HT. Sta- bility of P3HTs during repeated charge–discharge cycles, also found to increase with increase in regioregularity. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction In recent years there has been a thrust on conducting poly- mers based supercapacitors because of two important points. First, in conducting polymer, entire bulk of the polymer is uti- lized for charge storage which results high specific capacitance and; second, conducting polymers are cheaper and easier to syn- thesize compared to noble metal oxides [1,2]. Among various conducting polymers used for the supercapacitor applications [3], polythiophenes have attracted much attention, due to their excel- lent thermal and environmental stability [4]. A large number of poly(alkylthiophene)s (P3AT)s have been used in supercapacitors and batteries, since they can be positively as well as negatively doped [3]. One of the important properties of P3AT is regioregular- ity. 3-alkylthiophenes are non symmetric and hence during poly- merization, thiophene rings can be coupled between 2 and 5 posi- tions in three possible ways, head-to-tail (HT), head-to-head (HH) and tail-to-tail (TT) manner. Regioregularity denotes the percent- age of HT couplings in polymer [4–6]. Increasing the regioregularity in the polymer chain results in longer conjugation length with high tendency to self assemble into highly ordered and partially crys- talline structure and have enhanced conductivity [7,8]. The impor- tance of regioregularity has been explored in the fields of organic field effect transistors, organic photovoltaics, organic light emitting diodes, etc. [9,10]. Regioregular poly(3-hexylthiophene) (P3HT) ∗ Corresponding author. Tel.: +91 251 2623036; fax: +91 251 2623004. E-mail addresses: asit samui@yahoo.com, absamui@gmail.com (A.B. Samui). is one of the most widely used polymers in organic electronics [11–15]. However, this material has not been studied extensively for energy storage devices. Further, the effect of regioregularity has not been explored extensively in the field of supercapacitors. To the best of our knowledge, there is no report on the systematic study of the effect of regioregularity on specific capacitance of P3HT. In the present paper, we have carried out a study of the effect of regioregularity on the specific capacitance of P3HT. Therefore, P3HTs with three different regioregularities have been synthesized and characterized. Structural analysis of P3HTs was performed by nuclear magnetic resonance (NMR), UV–Vis spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. Electrochemical performance of P3HTs was studied by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy as a function of regioregularity. 2. Experimental 2.1. Materials 3-Hexylthiophene and 2,5-dibromo-3-hexylthiophene were synthesized following the reported procedure [5]. Isopropyl mag- nesium chloride (etherial solution), ferric chloride, hydrazine hydrate, Et 4 NBF 4 and Ni(dppp)Cl 2 (where dppp is 1,3 diphenyl phosphino propane) were purchased from Aldrich Chemicals. All solvents were purchased from Sd fine chemicals, India and dried by conventional methods prior to use. 0013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2012.02.085