D.C. conductivity and thermal aging of conducting zeolite/polyaniline and zeolite/polypyrrole blends E. Vitoratos a , S. Sakkopoulos a, * , E. Dalas b , P. Malkaj c , Ch. Anestis a a Department of Physics, University of Patras, 265 00 Patras, Greece b Department of Chemistry, University of Patras, 265 00 Patras, Greece c Department of Physics, Polytechnic University of Tirana, Tirana, Albania Received 5 October 2006; received in revised form 8 November 2006; accepted 7 December 2006 Available online 20 December 2006 Abstract The d.c. conductivity r of zeolite/polyaniline (PANI) and zeolite/polypyrrole (PPy) blends of various concentrations in zeolite was measured from 80 to 320 K. Moreover, the thermal degradation of r was studied by heating the blends at 70 °C under environmental conditions for times between 0 and 600 h approximately. The experimental results indicate a structure of the granular metal type, in which conductive grains are randomly distributed in an insulating matrix and thermal degradation is due to the shrinking of them. As the zeolite content increases in the zeolite/PPy blends, the separation between the conductive grains decreases, the conductivity increases and the thermal stability of the blends improves. On the contrary, the behaviour of the zeolite/PANI samples is almost inde- pendent from the zeolite content. An explanation of this difference is proposed based on the crystalline character of the conductive grains in PANI in contrast to the amorphous grains of PPy. Ó 2006 Elsevier B.V. All rights reserved. PACS: 71.20.Rv; 72.80.Le; 72.80.Ng; 72.80.Tm Keywords: Conducting polymers; Polyaniline; Polypyrrole; Zeolite; Blends; Aging 1. Introduction Aging, i.e. the irreversible decrease of the electrical con- ductivity of conducting polymers with time under environ- mental conditions, is the main restriction for their use in technological applications, as in antistatic coatings, solid- state batteries, solar cells, electronic devices, etc. Aging is a complicated process involving the loss of dopant, chlori- nation of the rings, oxidation, hydrolysis and crosslinking of the chains [1]. As it is very important to understand this undesirable degradation in order to find ways to delay it, a great effort has been done to this direction [2–4]. Recently, inorganic solids with layered and porous structure have been used to confine and encapsulate into them conducting polymers to obtain nanocomposite materials with novel physico-chemical properties [5,6]. Especially, the structure of zeolite, involving pores, channels and cages of different shapes and dimensions of the nanometer order of magni- tude, is expected to protect the polymer from degradation, in which oxygen and moisture from the atmospheric air play a leading part. The isolation of the functional con- ducting polymer chains into the porous and the improving of their alignment are expected to decelerate aging and to increase their electrical conductivity. Moreover, the acidity of the zeolite surface ensures the excellent adhesion of the two materials and a zeolite/conducting polymer system combines the fast electronic mobility of the polymer with the capability of the zeolite to accommodate exchangeable cations into its structure [7]. To investigate the influence of zeolite on the aging rate and on the conductivity of PANI and PPy, zeolite/conductive polymer samples with different zeolite content were prepared and their d.c. conductivity 1567-1739/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2006.12.001 * Corresponding author. E-mail address: sakkop@physics.upatras.gr (S. Sakkopoulos). www.elsevier.com/locate/cap www.kps.or.kr Current Applied Physics 7 (2007) 578–581