ELECTROCHEMICAL BEHAVIOR AND CONSTITUTION OF POLYANILINE AND POLYACETYLENE (POLYMERS, CONDUCTING, BATTERIES, ELECTROACTIVE, EMERALDINE)
The objectives of the present investigation were (1) to chemically synthesize and characterize an analytically pure form of polyaniline in the emeraldine oxidation state and to prove that it was similar in chemical constitution to a form of polyaniline synthesized electro- chemically, (2) to chemically characterize the emeraldine form of polyaniline as a cathode-active material in aqueous and non-aqueous electrolytes, (3) to electrochemically characterize emeraldine form of polyaniline as an anode-active material in aqueous electrolytes, (4) to electrochemically characterize partially oxidized (p-doped) polyacetylene as a cathode-active material in aqueous acidic elec- trolytes. The most significant results and conclusions are as follows.^ (i) The emeraldine base form of polyaniline having the ideal struc- ture ((C(,6)H(,4))-N(H)-(C(,6)H(,4))-N(H))(,a)((C(,6)H(,4))-N=(C(,6)H(,4))=N-)(,b) (,x) where a = b, can be synthesized chemically in an analytically pure form. However electrochemical studies show that the actual composition of the material has, a = 0.53 and b = 0.47.^ (ii) Spectral techniques (FTIR, XPS and Mass spectroscopy), thermogrammetric and electrochemical techniques (cyclic voltam- metry and chronopotentiometry) were used for constitutional charac- terization of emeraldine salts and emeraldine base. FTIR spectros- copy and cyclic voltammetry indicate a constitutional similarity with emeraldine.HCl synthesized chemically and a form of polyaniline synthesized electrochemically.^ (iii) The emeraldine salt form of polyaniline is stable in the metal- lic conducting regime on exposure to laboratory air for over three months.^ (iv) Coulombic efficiencies over 98% and excellent retention in capacity upon cycling the emeraldine base/1 M ZnCl(,2) (aq.)/Zn cell indicate that emeraldine base acts as an excellent reversible cathode in aqueous electrolytes. The calculated capacity (107.2 WHrs/Kg) is identical to that obtained experimentally.^ (v) Electrochemical characterization of emeraldine base/1 M LiClO(,4) (pc)/Li cell indicates that chemically synthesized emeraldine base acts as an excellent reversible cathode in non-aqueous electrolytes.^ (vi) Electrochemical characterization of PbO(,2)/4 M H(,2)SO(,4)/emer- aldine.H(,2)SO(,4) indicates that emeraldine.H(,2)SO(,4) acts as a reasonably good anode in aqueous electrolytes.^ (vii) Polyacetylene, (CH)(,x) can be electrochemically oxidized to the metallic conducting regime in 7.4 M aqueous HBF(,4). Recycling studies in a (CH('+0.01)(BF(,4))(,0.01))(,x)/7.4 M HBF(,4) + 0.5 M Pb(BF(,4))(,2)/Pb cell indicate a gradual decrease in electroactivity of the polyacety- lene species. This is believed to be due to the partial hydrolysis of the (CH('+y))(,x) carbonium ion in 7.4 M aqueous HBF(,4). Possible improvements are discussed. ^
NANAYAKKARA L. D SOMASIRI,
"ELECTROCHEMICAL BEHAVIOR AND CONSTITUTION OF POLYANILINE AND POLYACETYLENE (POLYMERS, CONDUCTING, BATTERIES, ELECTROACTIVE, EMERALDINE)"
(January 1, 1985).
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