Conductivity and thermal studies of blend polymer electrolytes based on PVAc–PMMA R. Baskaran a , S. Selvasekarapandian a, ⁎ , N. Kuwata b , J. Kawamura b , T. Hattori b a Solid State and Radiation Physics Lab, Department of Physics, Bharathiar University, Coimbatore-641 046, Tamil Nadu, 641 046, India b Institute of Multi Disciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan Received 1 July 2005; accepted 10 April 2006 Abstract The polymer electrolytes comprising blend of poly(vinyl acetate) (PVAc) and poly(methylmethacrylate) (PMMA) as a host polymer and LiClO 4 as a dopant are prepared by solution casting technique. The amorphous nature of the polymer–salt complex has been confirmed by XRD analysis. The DSC thermograms show two T g 's for PVAc–PMMA blend. A decrease in T g with the LiClO 4 content reveals the increase of segmental motion. Conductance spectra results are found to obey the Jonscher's power law and the maximum dc conductivity value is found to be 1.76 × 10 - 3 S cm - 1 at 303K for the blend polymer complex with 20wt.% LiClO 4 , which is suitable for the Li rechargeable batteries. The conductivity–temperature plots are found to follow an Arrhenius nature. The dc conductivity is found to increase with increase of salt concentration in the blend polymer complexes. © 2006 Elsevier B.V. All rights reserved. Keywords: PVAc; Blend polymers; Ionic conductivity; DSC analysis; Conductance spectra; Polymer electrolytes; Arrhenius behaviour 1. Introduction Rechargeable lithium polymer batteries using polymer electrolytes are currently being studied widely [1,2]. The recent attention to polymer electrolytes is focused on high ionic conductivity as well as good mechanical properties. A number of methods have been reported for improving the mechanical and morphological characteristics of polymer electrolytes in the higher temperature range, and for improving conductivity in the lower temperature range. These include the use of cross linking agents [3] to form networks, use of grafts [4], blending polymers [5], block copolymers [6] and addition of inert fillers to the polymer electrolytes [7]. Blending of two polymers is easy method for preparation and to control the physical properties within the compositional regime. Many blend electrolytes have been reported based on PEO-PAN [8],P (VdF-HFP)-PVAc [9], PVC-PMMA [10] and so on. In the present study, ionic conductivities of PVAc–PMMA blend polymer electrolyte films containing three different concentrations of lithium salt (LiClO 4 ) are studied by conductance spectra analysis in the temperature range 303– 373K. Differential scanning calorimetry (DSC) aims to study the thermal stability of the blend polymer electrolytes. XRD analysis has been carried out to confirm amorphous nature of the blend polymer–salt complex. 2. Experimental The polymer electrolytes composed of a blend of poly(vinyl acetate) PVAc (Himedia) and poly(methylmethacrylate) PMMA (Aldrich) as host polymers and LiClO 4 (Himedia) as a dopant have been prepared by solution casting technique with tetrahydrofuran (THF) (s.d. fine) as solvent. The polymer blend ratio is fixed as 70:30wt.% (PVAc/PMMA) on the basis of conductivity and mechanical stability of the film. Polymer blend electrolytes of various compositions are prepared by varying the salt and polymer concentrations (Table 1) in the stoichiometric ratio. Conductivity measurements are carried out using a HIOKI-3532 LCZ meter in the frequency range of 42Hz–5 MHz over a temperature range of 303–373 K. The Cu- Kα line has been used for XRD measurements by the usual θ– Solid State Ionics 177 (2006) 2679 – 2682 www.elsevier.com/locate/ssi ⁎ Corresponding author. Tel.: +91 422 2422222x422; fax: +91 422 2422387. E-mail address: sekarapandian@yahoo.com (S. Selvasekarapandian). 0167-2738/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.ssi.2006.04.013