Synthetic Metals 159 (2009) 2519–2524 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Polyaniline composite by in situ polymerization on a swollen PVA gel Sarbani Adhikari, P. Banerji ∗ Materials Science Centre, Indian Institute of Technology, Kharagpur 721302, India article info Article history: Received 26 June 2009 Received in revised form 19 August 2009 Accepted 24 August 2009 Available online 17 September 2009 Keywords: Polyaniline Hydrogel Electrical conductivity FTIR abstract Interpenetrating polyaniline (PANI) formation in a 3D network of poly(vinyl alcohol) (PVA) hydrogel was developed. Polymerization was effected by immersing swollen PVA hydrogel previously soaked with ammonium persulfate (APS) in 1 M HCl solution of aniline hydrochloride (AnHCl). Gradual transformation of the swollen gel from colorless transparent gel to an opaque green color indicated the formation of PANI emeraldine salt (ES) on the surface and bulk of the PVA gel matrix. Characterization by UV–vis spectra, ATR-FTIR spectra and X-ray diffraction analyses supported the formation of PANI–PVA composite film. The surface morphology of the film was studied by FESEM. Electrical conductivity of the film was measured by four-probe method. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Polyaniline has attracted a lot of attention in the last decade because of its ease of synthesis, good environmental stability [1,2] high conductivity [3,4] and reversible doping/dedoping process compared to other conductive polymers [5,6]. Synthesis of nano- materials with well controlled morphology and size is a key issue in current nanoscience research because they are the key parameters to determine the optical, electronic, magnetic, and chemical prop- erties [7–13]. PANI nanostructures have recently received much attention because the high surface area of these materials is of inter- est for the development of actuators, drug delivery systems, field emission displays, gas sensors, and biosensors [14–16]. PANI nanos- tructures, such as nanofibers/tubes, can be made by introducing ‘structural directors’ into the chemical polymerization bath. These structural directors include ‘soft templates’ such as surfactants [17], organic dopants [18] or polyelectrolytes [19] that assist in the self-assembly of the PANI nanostructures and ‘hard templates’ such as porous membranes [20] or zeolites [21]. Films containing PANI nanofibers can also be made by using the electrospinning [22] or electrochemical method to control the polymerization rate [23]. In spite of its excellent thermal and environmental stabil- ity, poor processability due to insolubility and brittleness limit its commercial applications. PANI can be made more processable in the composite form with another water soluble polymer such as PVA, poly(vinyl pyrrolidone), poly(acrylic acid) and poly(styrene sulfonic acid) (PSSA) which are used as stabilizers [24]. A function- ∗ Corresponding author. Tel.: +91 3222 283984; fax: +91 3222 255303. E-mail addresses: pallab@matsc.iitkgp.ernet.in, pallab banerji@yahoo.com (P. Banerji). alized protonic acid can be added into the composites to chemically polymerize PANI. The PANI dispersion can then be cast to form composite film containing PANI nanoparticles [24]. Trivedi et al. [25], and recently Gangopadhyay et al. [26] have reported the preparation of a homogeneously dispersed PANI in an aqueous solution of PVA having stability for almost 6 months at room temperature. PANI–PVA composite exhibits microwave shielding property over the X-band [26] and is used in electrical connec- tors for display devices [27] and as a sensor for humidity [28]. Ali et al. [29] have synthesized PANI nanoparticles dispersed in PVA films using radiation technique. Dupare et al. [30] have synthesized PANI–PVA blend films by oxidative polymerization using chemical synthesis route and they have used the blend films for ammonia gas sensing. PANI and its blends with PVA and PVA–Cu (II) com- plex were synthesized by Murugesan and Subramanian [31] by in situ chemical oxidative polymerization technique with potassium perdisulfate (PDS) oxidant in aqueous sulfuric acid medium. Bhadra and Sarkar [32] have prepared ordered PANI nanorod arrays by dis- persion polymerization of aniline in PVA. Amarnath et al. [33] have reported preparation of PANI dispersion in water using acacia gum (ACACIA). They observed that a blend of PVA with the composite PANI—(60 wt.%) ACACIA was highly conducting even for very low PANI with conductivity in the range 10 -4 S cm -1 to 10 -5 S cm -1 . In this study we report the synthesis of nanostructured PANI on maleic acid (MA) cross-linked PVA (MA-PVA) by oxidative poly- merization of AnHCl using APS as oxidant. The novelty of this investigation lies in the in situ deposition of nanostructured PANI emeraldine salt on APS soaked and swollen cross-linked PVA sub- strate by the polymerization of AnHCl both on the surface and bulk of PVA hydrogel thus avoiding the problem of PANI insolubil- ity. The obtained nanostructured materials were characterized by FESEM, FTIR and UV–vis spectroscopy, X-ray diffraction and elec- 0379-6779/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2009.08.050