Studies on a new proton conducting polymer system: poly(ethylene succinate) + NH 4 ClO 4 Neelam Srivastava a , Suresh Chandra b, * a Department of Physics, Mahila Vidyalaya Degree College Aminabad, Lucknow 226 018 India b Department of Physics, Banaras Hindu University, Varanasi 221 005, India Received 23 June 1998; received in revised form 14 January 1999; accepted 29 January 1999 Abstract Poly(ethylene succinate) complexed with dierent amounts of NH 4 ClO 4 is investigated as a possible proton conducting polymer. DTA, XRD, IR and complex impedance spectroscopy techniques have been used for the structural and ion transport studies. The conductivity as a function of composition, temperature and relative humidity are reported. The paper also reports the eect of addition of a plasticiser poly(ethylene glycol) (PEG) of dierent molecular weights on the conductivity. Higher conductivity is obtained for materials in which the added plasticiser PEG has a lower molecular weight. # 1999 Elsevier Science Ltd. All rights reserved. 1. Introduction Polymer-salt complexes has been an area of interest since Wright [1,2] and Armand [3,4] ®rst reported them as possible ion conducting polymers (for review see [5±22]). Recently, the proton conducting electro- lytes have received great attention due to their appli- cations in devices such as a fuel cells, sensors etc. These materials are prepared by doping appropriate salt or acid in a suitable polymer matrix. Generally, the polymers with polar groups like poly(ethylene oxide) (PEO), poly(ethylene imine) (PEI), poly(vinyl pyrrolidone) (PVP) have been used as the host polymer matrices and dierent ammonium salts and acids as the dopant materials (for review see [13±23]). The basic requirements for the host polymer matrix are: (1) low glass transition temperature, (2) low cohesive energy and (3) ¯exible backbone and presence of polar groups [6,7,24]. The poly(ethylene succinate) (PESc) satis®es most of these criteria. It has the added advan- tage that it is insoluble in water and hence will be less susceptible to high humidity related degradation. But surprisingly, this material received less attention than what is called for. Only some Li + and Na + ion con- ducting complexes [22±28] have been reported. Recently we have reported H + ion conduction in PESc:NH 4 SCN system [20]. The present paper dis- cusses preparation and characterisation of another pro- ton conducting polymer salt complex using PESc as host polymer matrix and NH 4 ClO 4 as dopant salt. The room temperature conductivity of pure PESc is 0 10 11 S/cm but complexing it with NH 4 ClO 4 raised its con- ductivity up to 0 10 7 S/cm which has been shown in this paper as due to the H + ion transport. This paper also reports the results of our eorts to increase the conductivity of the PESc:NH 4 ClO 4 system by adding dierent amounts of poly(ethylene glycol) (PEG) of dierent molecular weights. The best conductivity obtained for our plasticised sample was 10 5 S/cm. European Polymer Journal 36 (2000) 421±433 0014-3057/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0014-3057(99)00056-7 * Corresponding author. Tel.: +91-542-312-299; fax: +91- 542-317074.