Montmorillonite intercalated by conducting polyanilines L. Kulha ´ nkova ´ a,n , J. Tokarsky ´ a , P. Peikertova ´ a , K. Mamulova ´ Kutla ´ kova ´ a , L. Iva ´ nek b , P. ˇ Capkova ´ a a Nanotechnology centre, V ˇ SB-Technical University of Ostrava, 17. listopadu 15, 70833 Ostrava, Czech Republic b Faculty of Electrical Engineering and Computer Science, V ˇ SB-Technical University of Ostrava, 17. listopadu 15, 70833 Ostrava, Czech Republic article info Available online 25 January 2012 Keywords: A. Nanostructures A. Polymers B. Chemical synthesis C. X-ray diffraction D. Electrical conductivity abstract Structure and conductivity of nanocomposite conducting polymer/montmorillonite have been inves- tigated for samples prepared by the polymerization of aniline hydrochloride with ammonium peroxodisulfate in aqueous suspension of montmorillonite. Samples were characterized by combina- tion of X-ray powder diffraction (XRPD), IR spectroscopy and electrical conductivity measurements. Structure analysis based on combination of molecular modeling and experiment (XRPD and IR spectroscopy) revealed the structure of nanocomposite, including the interlayer structure of montmor- illonite, and helped to understand the processes during nanocomposite preparation. Partial intercala- tion of polyaniline oligomers into the interlayer space of montmorillonite led to the large inhomogeneity of interlayer structure, which results in dramatic decrease of the electrical conductivity of nanocomposite in comparison with pure polyaniline. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Conducting polymers (CP) have been systematically studied during the last two decades, as the range of potential uses covers simple and cheap microelectronic parts, electrochromic devices, electromagnetic shielding, analytical separations, marker parti- cles and sensors [1,2]. Anyway the topical research field still expands to new directions. Nanocomposite CP/phyllosilicate, sometimes referred to as CP/clay, represents one of the new fields in novel materials design, emerging in the last several years [3,4]. In addition to the clays, other types of porous substrates are also used [5]. It is known that interaction of organic dyes with the phyllosilicate negatively charged layers leads to the dramatic change of spectral properties of organic dyes [6–8]. This spectral change of intercalated dyes is strongly dependent on the layer charge of phyllosilicate matrix. This fact enables the tuning of photoluminiscence using two methods: (1) by a choice of suitable dye/clay combination (montmorillonite, vermiculite, etc.) and (2) by a tuning of layer charge of phyllosilicate matrix via preintercalation of lithium cations [9]. The present state of research and our experience with intercalation of organic dyes led us to the conclusions that the interaction of CP and phyllo- silicate in the pure intercalated structures deserves more atten- tion with respect to the design of novel electro-active and photo- active materials [6,9]. Two different ways of polyaniline/montmorillonite (PANI/ MMT) nanocomposite preparation have been worked out by Bober et al. [3]: one- and two-step preparation methods. As the one-step method led to higher conductivity, we decided to use this method in this study. The aim of present work is to analyze the interlayer structure of MMT and the effect of charged silicate layers on the molecular structure of PANI. Combination of X-ray powder diffraction (XRPD), Fourier transformed infrared spectro- scopy (FTIR), thermogravimetric analysis (TGA) and molecular modeling in Materials Studio modeling environment has been used for the complex structure analysis. 2. Sample preparation In this study we used the following materials: (1) montmor- illonite (MMT, from Ivanc ˇice, Czech Republic), structural formula (Ca 0.24 K 0.06 Na 0.09 Mg 0.10 )(Al 2.52 Fe 3 þ 0.54 Mg 0.90 Ti 0.04 )(Si 7.96 Al 0.04 )O 20 (OH) 4 , (2) aniline hydrochloride (Fisher Scientific, UK) and (3) ammonium peroxodisulfate (Lach-Ner, Czech Republic). One step method of preparation has been chosen in this work, as according to [3] it led to higher conductivity. Further motivation for one step method is the low cost technology in future practical applications; therefore the natural Ca-montmorillonite has been used in the pristine form. The composite was prepared by the polymerization of aniline hydrochloride with ammonium peroxodi- sulfate in aqueous suspension of MMT at 20 1C. MMT was sus- pended in freshly prepared aqueous reaction mixture (0.100 dm 3 ) containing 2.59 g aniline hydrochloride (0.2 mol dm 3 ) and 5.71 g ammonium peroxodisulfate (0.25 mol dm 3 ). The polymerization of Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jpcs Journal of Physics and Chemistry of Solids 0022-3697/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpcs.2011.11.043 n Corresponding author. E-mail address: lenka.kulhankova@vsb.cz (L. Kulha ´ nkova ´). Journal of Physics and Chemistry of Solids 73 (2012) 1530–1533