Conducting Polymers and Polymer Electrolytes

Abstract

UMI Number: U547216All rights reserved INFORMATION TO ALL U SE R S The quality of this reproduction is d ep endent upon the quality of the copy submitted.In the unlikely event that the author did not sen d a com plete manuscript and there are m issing p a g es, th e se will be noted. Also, if material had to be removed, a note will indicate the deletion. Disscrrlation PublishingUMI CONDUCTING POLYMERS AND POLYMER ELECTROLYTESby Walkiria Santos Schlindwein Abstract Polymers are mostly used as insulator materials. Since the late sixties, two new classes of polymeric materials possessing either ionic or electronic conductivities have been extensively studied. The work carried out in this thesis concerns of the study of polymer electrolytes based on poly (ethylene oxide) (PEO) complexed with divalent salts (ionic conductors) and polypyrroles (PPy) electrochem icdly and chemically prepared (electronic conductors). DiÉerent techniques were used to study their properties including Differential Scanning Calorimetry 03SC), Variable Temperature Polarising M icroscopy (VTPM), Extended X-ray Absorption Fine Structure (EXAFS), a.c. Impedance, Cyclic Voltammetry, and Fourier Transform Infra-Red Spectroscopy (FTIR).W ater-cast film s o f P E 0n:Z nX 2 (X = Cl, Br, I) were prepared at a range of stoichiometries. The effects of either residual presence of water or thermal treatment related to the formation of high melting crystalline materials were investigated. The morphology of the zinc halides films differs from similar films cast from acetonitrile/methanol mixtures. The presence of high melting crystalline material in the water cast samples is influenced mostly by the concentration, type of anion and drying procedure applied to the samples. The high melting crystalline materials in the zinc samples are more affected by the drying regime. In some cases, solvent effects can be removed by using a high temperature (e.g. 180°C) drying regime. The presence of water normally depresses the melting temperature of the crystalline structures.Films of PE0 n:CaBr2 and PE0 n:NiBr2 cast from water were also examined. The high melting crystalline materials in the calcium samples are more affected by the presence of water. The nickel samples are highly crystalline and the presence of high melting material does not seem to be influenced by either the presence of solvent or the drying procedure.EXAFS was used as a suitable technique to probe the local structure surrounding the cation. The results of the zinc halide samples gave some indication o f the interionic and polym er-cation interactions. It was demonstrated that the halogen provides the most substantial contribution for the total EXAFS spectrum and the oxygen contribution is much less significant, except in the case of PEOn:ZnCl2 samples. This could be due to the size of the nearest neighbour atoms and/or to the interaction polymer-cation. The presence of neutral "ion pairing" is suggested for the PEOn:ZnBr2 samples. The EXAFS results for the samples containing NiBr2 indicated a stro...