Synthetic Metals 146 (2004) 57–62 Novel flexible, freestanding and transparent organic/inorganic hybrid materials formed between polyaniline and polyphosphate gel Eryza Guimar˜ aes de Castro a , Aldo Jos´ e Gorgatti Zarbin a,∗ , Helinando P. de Oliveira b , Andr´ e Galembeck c a Departamento de Qu´ ımica, Universidade Federal do Paran´ a (UFPR), CP 19081, CEP 81531, Curitiba, PR, Brazil b Departamento de F´ ısica, Universidade Federal de Pernambuco (UFPE), CEP 50670-901, Recife, PE, Brazil c Departamento de Qu´ ımica Fundamental, Universidade Federal de Pernambuco (UFPE), CEP 50670-901, Recife, PE, Brazil Received 23 February 2004; received in revised form 3 May 2004; accepted 7 June 2004 Available online 5 August 2004 Abstract In this paper we report the synthesis and characterization of new polyaniline/polyphosphate hybrid materials. The synthetic approach involves a single-step procedure in which the polyphosphate inorganic host structure (arising from a sol–gel transition) develops first, providing a restricted environment in which the conducting polymer is entrapped within the gel network. Polyaniline was formed as the green, conducting emeraldine salt form. The samples were characterized by thermogravimetric analysis and UV–vis, Raman, EPR and 31 P-MAS- NMR spectroscopies. We have synthesized homogeneous, flexible, freestanding and transparent materials in which the conducting polymer presents a coiled conformation typical of primary doped polyaniline. Upon exposition to ammonia vapors the polymer can be converted to the emeraldine base form, which can be reverted by exposition to HCl vapors. Powdered samples present dc conductivities up to 0.2 S cm -1 . © 2004 Elsevier B.V. All rights reserved. Keywords: Organic/inorganic hybrid; Polyaniline; Polyphosphate; Sol–gel process 1. Introduction The synthesis of organic/inorganic hybrid materials is a very important and expanding area, which has leaded to new materials with unprecedented optical, electronic and mechan- ical properties [1–10]. A very important class of these materials presents con- ducting polymers as the organic fraction [11–22]. Nanocom- posites obtained by the encapsulation of conducting polymers within void spaces of inorganic host matrices such as pores, cavities, tunnels, micelles and interlayer domains have been described in the literature [18,19]. We have recently prepared polypyrrole and polyaniline hybrids with several inorganic matrices like porous glasses [20], layered materials [21] and three-dimensional framework materials [22]. ∗ Corresponding author. Tel.: +55 41 3613297; fax: +55 41 3613186. E-mail address: aldo@quimica.ufpr.br (A.J.G. Zarbin). The sol–gel process provides a very versatile path to syn- thesize hybrid materials, in such a way the inorganic and organic components can be mixed at the nanoscopic level. In most cases, the inorganic phase develops from hydrolysis and condensation reactions of alkoxide precursors, leading to a covalently bonded network. Low temperature reactions and the use of organic solvents allow for the incorporation of the organic phase [23–26]. Our research group has been exploring the use of alu- minum polyphosphate gels (APP) as an inorganic host for hy- brid materials [27–29]. In this case, the gelation proceeds due to the association of polyphosphate polyanions linear chains and Al 3+ ions in aqueous solution, leading to a supramolec- ular ionic swollen network [30]. Hence, the system cohesion derives from electrostatic interactions rather covalent bonds. APP gels are transparent to visible light, permeable to wa- ter and hydrophilic vapors and may be synthesized at or near room temperature within a few days. They can be processed 0379-6779/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2004.06.018