2600
Ind. Eng. Chem. Res. 1994,33, 2600-2606
MATERIALS AND INTERFACES Degradation Kinetics of Polyaniline Base and Sulfonated Polyaniline Tsung-Chieh Tsai? D. Alan Tree,’ and Martin S. High* 423 Engineering North, School of Chemical Engineering, Oklahoma State Uniuersity, Stillwater, Oklahoma 74078
Polyaniline (PA) and sulfonated PA samples were prepared and subjected to thermogravimetic analysis (TGA) in both vacuum and inert atmospheres. The gas phase degradation products were analyzed with gas chromatography (GC).The thermal degradation of polyaniline base was found to follow apparent second-order reaction kinetics with an activation energy of 30 kcallmol. Two major weight loss regimes were observed in the TGA curve of sulfonated polyaniline. The first regime showed apparent fourth-order reaction kinetics with a n activation energy of 47 kcallmol; the second showed a n apparent third-order reaction with a n activation energy of 32 kcal/mol. The degradation products from PA and sulfonated PA were compared to those predicted by a previously proposed degradation mechanism for polyaniline hydrochloride. The absence of key degradation products indicates that sulfonated PA does not have the same degradation mechanism as polyaniline hydrochloride.
Introduction
or
The most promising, environmentally stable, conducting polymeric material appears to be polyaniline (PA) which was discovered in 1910 and rediscovered by MacDiarmid in 1984 (MacDiarmid et al., 1984). Potential uses of PA include microelectronic devices, electrodes, light weight battery components, thermal history sensors, electrochromic displays, static free packing materials (Caja et al., 1984; Maxfield et al., 1985; Kitani et al., 1986; MacDiarmid et al., 1985, 1987a; Mengoli et al., 1987; Osaka et al., 1989; Scrosati, 1989; McManus et al., 1987; Kobayashi et al., 1984a; Batich et al., 1984; Kobayashi et al., 1984b),ion exchange resin (Paul et al., 19851, and electrocatalytic applications (Kost and Bartak, 1988). PA base has the general formula:
where y indicates the fraction of reduced mers and 1 y gives the fraction of oxidized mers. The case of y =
0.5 is called emeraldine base and can be doped externally to form emeraldine hydrochloride that has the formula
H
L ‘
H
CI -
H
CI-
’
J
Emeraldine base can also be internally substituted by sulfonic acid, to produce sulfonated emeraldine:
In either case, the electrical conductivity can increase by as much as 11orders of magnitude (Hagiwara et al., 1988). A key to full exploitation of PA is a quantitative understanding of the thermal stability. Significant work has been conducted on the degradation of polyaniline under anodic potential in an aqueous environment (Kobayashi et al., 1984b; Hand and Nelson, 1974; Stilwell and Park, 1988, 1989; Hagiwara et al., 1988; LaCroix and Diaz, 1988; Wei and Hsueh, 1989) and on the loss of electrical properties as a result of thermal history. The primary goal of this study was t o determine the thermal degradation kinetics parameters which will be required in the design of practical devices. In addition, the gaseous degradation products were examined by gas chromatography, which allowed some significant insight into the degradation mechanism.
Data Analysis
* Author t o whom correspondence should be addressed. E-mail:
[email protected]. t E-mail:
[email protected].
[email protected]. f
The Ozawa (1965) method, was used to reduce the thermogravimetric analysis (TGA) data to reaction parameters. The rate of decomposition was assumed to have the form
0888-5885/94/2633-260~~~4.50f0 0 1994 American Chemical Society
Ind. Eng. Chem. Res., Vol. 33, No. 11,1994 2601
--=kw dW dt
(5)
The reaction order was initially assumed to be constant. The temperature dependence was assumed to reside only in the rate constant via an Arrhenius form, hence
-dW = A e x p-AE [w)v dt
+
Since T = TO at, at a constant heating rate of a, dT = adt which can be substituted into eq 6 and integrated t o yield (7) Generally, degradation reactions are very slow at subambient temperatures so that the lower limit of the integral on the right hand side of eq 7, TO, can be approximated to be zero. Integration of the right hand side of eq 7 results in an infinite series of the form
-AE
Doyle (1961) represented the integral with the expression
(9) and showed that the function p can be approximated by (10) Doyle obtained the constants of eq 10 (c and m ) by truncating the infinite series on the right hand side of eq 8 after the first term in parentheses. Doyle's approximation represents the integral well provided that AEIRT L 20. In this study, Doyle's approximation was extended by numerically integrating the left hand side of eq 9 and linearly regressing the constants c and m, which gave a good approximation for AEIRT L 13. The extension was necessary due to the relatively high temperatures encountered. Substitution of eq 9 into eq 7 yields
A A E AE
wdW
-iwo
=
xp(m)
(11)
For a given value of W, the left hand side of eq 11 is a constant and is independent of the heating rate. Therefore, for a given weight fraction, the right hand side of eq 11is evaluated a t T = TI for a heating rate of a1 and must be equal to the right hand side of eq 11 evaluated a t T = T2 for the heating rate u2. That is
A A E AE A A E AE -Pa,R (RT,) =-Pa$ (RT,) - "'
(12)
provided that W is constant. Using Doyle's approxima-
Table 1. Some Typical Forms of g(W) and -j;-dW/g(W) type of reaction 0th order 1st order 2nd order 3rd order 4th order
R(w)
(AAE/aR)p(AE/Ri")
1 W
wo - w In(Wdw) 1/w - 1/wo 2JW - 2/Wo2 3JW - 3/wO3
W W w4
tion and taking the logarithm, the following linear equation can be obtained -log,, a, - 0.4881 AE =
RTl
-log,, a2 - 0.4881 AE = ... (13) RT2
The activation energy can be obtained from the slope of a loglo a versus the reciprocal absolute temperature plot at constant W. Once AE has been determined, the right hand side of eq 11can be evaluated except for A. By plotting W as a function of log{(AEluR)p(AEIRT)}, a curve is obtained which should superimpose when shifted onto one of the curves given in Table 1,thereby determining the reaction order. The length of the lateral shift is equal to loglo A. In addition to the Ozawa method, two differential methods by Anderson and Freeman (1961) and Freeman and Carroll (1958) and one other integral method by MacCallum and Tanner (1970) were considered. The differential methods required greater precision than normally allowed by TGA data. The Anderson and Freeman method requires an extrapolation of Alog(dw1 dt) as a function of A(1og W,) to A(1og W,.) = 0 in order to determine the activation energy. The Anderson and Freeman method produced inconsistent and unreproduciable results due to the precision of the TGA data. The integral method of MacCallum and Tanner produced results consistent with the Ozawa method. However, the trial and error nature of the MacCallum and Tanner method made it more cumbersome and time consuming than the Ozawa method. Hence the Ozawa method was preferred.
Degradation Mechanism A degradation mechanism for emeraldine hydrochloride was proposed by Traore et al. (1991) who subjected emeraldine hydrochloride to thermogravimetric analysis (TGA) under high vacuum conditions in conjunction with thermal volatilization analysis (TVA). The first major weight loss in the TGA curve was observed at 230 "C and was attributed to hydrogen chloride gas evolution leading to the conclusion that the emeraldine hydrochloride had reverted to emeraldine base. Traore et al. proposed four separate backbone degradation reactions for emeraldine base degradation as shown in Figure 1. At temperatures of 520 "C-740 "C, a scission reaction (Figure l a ) between reduced mers occurs which produces ammonia, aniline, p-phenylenediamine, N-phenylaniline, and N-phenyl-1,4-benzenediamine. The remaining reduced repeating units fuse to form a carbazole group at higher temperatures and release hydrogen gas (Figure lb). The ladder structure of the carbazole groups can withstand higher temperatures without decomposition. Below 650 "C the oxidized repeating units undergo scission and rearrange to a
2602 Ind. Eng. Chem. Res., Vol. 33, No. 11, 1994
'H
H'
t
\
/
i
H2
i
Figure 1. Degradation mechanism for emeraldine base.
pyridine-based heterocycle (Figure IC).Above 730 "C the oxidized repeating units decompose to ammonia, methane, and acetylene (Figure Id). Therefore, the absence of ammonia in the gaseous degradation products would preclude reaction d as a possibility and cast doubt on the occurrence of reaction a. Yue et al. (1991) compared the thermostability of emeraldine hydrochloride and sulfonated emeraldine to their insulating base form and suggested that the degradation mechanism for sulfonated emeraldine was similar t o the hydrochloride emeraldine degradation mechanism but with sulfonic acid emission instead of hydrochloric acid emission. The gas chromatography experiment reported here was designed to test this hypothesis.
Equipment, Materials, and Procedures Linear low-density polyethylene (Quantum Corporation, GB 501-010) with a specific gravity of 0.919 was used as a model system to test the TGA and Ozawa methods. Emeraldine base was synthesized through an oxidative polymerization of aniline in HC1 solution by a stoichiometric equivalent of ammonium persulfate as described by MacDiarmid et al. (1987b) to avoid degradation during synthesis (Genies et al., 1985; Travers et al., 1985). The product was dried under vacuum at room temperature. Care was taken to remove impurities in the aniline by vacuum distillation. The dried polyaniline base product was a fine powder, insulating and black, but became dark purple in aqueous base and turquoise in aqueous acid as would be expected (MacDiarmid et al., 1987b). The DSC curve from 25 to 600 "C showed no evidence of first- or second-order phase transitions although an endothermic reaction was evident a t temperatures greater than 425 "C. Sulfonated emeraldine was prepared by the procedure described by Yue and Epstein (1990) and dried under vacuum. The product was dark green and conducting. The sulfonated emeraldine showed two endothermic DSC peaks at 180 and 265 "C. A Cahn TGA system was used in this study to determine the reaction kinetics. The samples were
subjected to a constant heating rate while the temperature and weight were measured and recorded for later reduction. The mass of each sample was determined t o three significant figures and was usually close to 8 mg. The kinetics data were taken under vacuum conditions. The gas chromatograph (GC) samples were obtained in separate runs by entraining the degradation products in an inert helium stream. In the GC runs, much larger samples (60-80 mg) were used to obtain higher and therefore more easily detectable concentrations of the degradation products. After the GC runs, a condensate was observed in the tube connecting the GC to the TGA furnace leading to the concern that condensate may have formed on the TGA hang down wire thereby introducing an error into the kinetics data. However, no significant residual mass was recorded in any TGA run from which kinetics data were taken. Therefore, no significant mass of condensate could have formed on the hang down wire during the runs made to determine the degradation kinetics. The gaseous degradation products from the TGA were analyzed with a Carle AGC 311H gas chromatograph. The analysis columns were packed with 60/80 mesh HayeSep C (10 ft x 118 in. SS) and a 45/60 mesh molecular sieve 5A (9 ft x 1/8 in. SS), respectively, and placed in series. The columns were arranged so that the HayeSep C could be back flushed and the molecular sieve could be bypassed. The HayeSep C column provided the separation of ammonia, acetylene, and carbon dioxide. The molecular sieve provided the separation of the light components, such as methane, carbon monoxide, and hydrogen. The GC was equipped with a hydrogen transfer system (operation temperature: 600 "C) that was used to give a positive deflection and improve the sensitivity and linearity to hydrogen concentration. The analysis procedure was t o elute the hydrogen first, then trap the carbon monoxide and methane in the molecular sieve column. At that time ammonia, acetylene, and carbon dioxide were analyzed by a thermal conductivity detector. After the ammonia was eluted from the HayeSep C column, the heavier components in the HayeSep column were back flushed. The components trapped in the molecular sieve column were then analyzed. Care was taken to prevent acetylene, carbon dioxide, and ammonia from entering the molecular sieve column since they would have been permanently adsorbed by the molecular sieve at the operation temperature. The oven temperature and helium flow rate were 100 "C and 30 mumin, respectively. Standard samples of hydrogen, oxygen, nitrogen, methane, carbon monoxide, carbon dioxide, and acetylene were obtained from Alltech and injected into the GC in order to (a) determine the retention time and (b) demonstrate the ability of the GC to detect these species.
Thermodegradation Products The TGA curves and degradation product concentrations for emeraldine base and sulfonated emeraldine are shown in Figures 2 and 3, respectively, for a heating rate of 6.67 "C/min in a helium atmosphere. The evolution rate is given as ppm of the original sample mass per minute. Hydrogen and methane were the only degradation products identified by GC for the emeraldine base while the sulfonated emeraldine also showed carbon monoxide. However, condensed reddish-yellow
Ind. Eng. Chem. Res., Vol. 33,No. 11, 1994 2603 120 j
o
t
Hz
1 "C/min
3OC/min
1
o
S0C/min
Calculated
0
200
400
600
800
1000
Temperature ("C) 600
Figure 2. Degradation product evolution rate and residual weight as a function of temperature for emeraldine base. 200
650
700
750
800
850
900
Temperature (K)
Figure 4. TGA curves of polyethylene. Table 2. Kinetic Parameters of the Decomposition of Polyethylene
W
\ S F
3
l 1 ' l l ' l l 1 1 1 '
0
200
400
600
' ' I l I I I ' ' I
800
0
1000
Temperature ("C)
Figure 3. Degradation product evolution rate and residual weight as a function of temperature for sulfonated emeraldine.
particles were observed on the relatively cold hang down tube wall above the TGA furnace. The masses of hydrogen and methane released from the samples were estimated to be 0.10 and 1.14 mg for emeraldine base and sulfonated emeraldine, respectively. The hydrogen and methane masses were relatively small compared to the respective 34.0 and 46.6 mg weight loss for emeraldine base and sulfonated emeraldine. Therefore, most of the degradation products which were not identified by the GC deposited on the cold hang down tube wall. The hydrogen and methane were not observed until after the major weight loss. The hydrogen component could have been released from the reduced repeating unit in emeraldine base as the chain fused to the ladder structure of the carbazole group, as proposed by Traore et al. as shown in Figure 1. This conclusion was supported by the high electric conductivity of the degradation residues, the structure of which was similar to the pyrolysis product of polyacrylonitrile (carbon fiber). The conductivity of polycarbazole was shown by O'Brien (1985) to be 10-100 S/cm-l. The methane component may have came from the oxidized mer as
0.95 0.90 0.85 0.80 0.75 0.70 0.65 0.60 0.55 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 mean
slope, K-l -25.2 -18.5 -16.1 -15.1 -14.6 -14.2 -13.9 -13.6 -13.2 -12.8 -12.5 -12.2 -12.1 -12.1 -12.1 -12.0 -12.0 -12.0 -13.2
AE,kcaYmol 109.7 80.2 70.1 65.8 63.4 61.9 60.5 59.1 57.3 55.8 54.4 53.2 52.4 52.5 52.4 52.2 52.1 52.2 57.5 61.2 A
log A 17.4 17.5 17.6 17.6 17.6 17.6 17.7 17.7 17.7 17.7 17.7 17.7 17.7 17.7 17.7 17.7 17.7 17.7 17.6 17.7 4.5 1017
proposed by Traore et al.; however, the absence of ammonia and acetylene indicate a different overall reaction mechanism.
Results and Discussion Polyethylene was tested first for the purpose of verifying the Ozawa integration method and the TGA techniques. Polyethylene thermodegradation was carried out from 25 to 625 "C under vacuum at four different heating rates: 1, 3, 5, and 10 "C/min. The activation energy, AE, as a function of W is presented in Table 2. The best representation of all the data was given by first-order kinetics with an activation energy of 61 kcal/mol which is in reasonable agreement with Madorsky (1952) and Oakes and Richards (1949) who reported first-order kinetics and activation energies of 68 f 5 kcaYmol and 60-70 kcaYmo1, respectively. The average value of A was 4.5 x 10'' min-'. The reaction order, activation energy, and preexponential factor were used to calculate the residue weight as a function of temperature and compared with the experimental data, as shown in Figure 4. The poorest agreement is in the early stages of degradation
2604 Ind. Eng. Chem. Res., Vol. 33, No. 11, 1994 I
c
3
3 "C/min
6.8 32
J c 6.4
c 28
8 6.2
0
20
40
80
60
100
W(%)
Figure 5. Activation energy and log A as a function of W (%) for emeraldine base. 120
450
1050
850
650
Temperature (K)
Figure 7. TGA curves of sulfonated emeraldine.
4
*
3
o
1 "C/min
6 0 ,
i
~~~
25 0
I
I
h
s n G
- Calculated
~
2
0 0
600
700
800
900
lo00
1100
I
1200
,
1
1
20
40
'
1
60
'
50
1
80
100
W(%)
Temperature (K) Figure 6. TGA curves of emeraldine base.
Figure 8. Activation energy and log A as a function of W (%) for sulfonated emeraldine.
where the activation energy and reaction order are too high. This result is consistent with Anderson and Freeman (1961), who reported the first 3% of weight loss to be zeroth-order with A E = 48 kcal/mol and the weight loss from 3-15% to be first-order with AE = 61 kcal/mol. After 35%weight loss, Anderson reported the reaction followed first-order kinetics with AI3 = 67 k c d mol, which is also consistent with the data given in Table 2. The Ozawa analysis was also applied t o emeraldine base, over the range of 25-925 "Cat heating rates of 1, 3, 5, and 10 "C/min. The reaction order, activation energy AE, and pre-exponential factor were determined to be second order, 31 kcaYmol, and 1.91 x lo6 min-l, respectively. The activation energy and pre-exponential factor as a function of weight fraction are given in Figure 5. Average values of A E and logA were found to be 30.4 kcal/mol and 6.44, respectively,and were used t o calculate the solid lines in Figure 6. Good agreement is seen between the experimental data and the calculated weight loss, except a t higher temperatures where a shift to a lower order reaction is indicated.
Sulfonated emeraldine thermodegradation was carried out under the same conditions as the emeraldine base. There were two major weight loss regimes in the TGA curves of sulfonated emeraldine, as shown in Figure 7. The first major weight loss, before 600 "C, was attributed t o the release of sulfonic groups (Yue et al., 1991) and the second major weight loss to chain degradation. The activation energy and log A were plotted as function of W (%) in Figure 8. The average kinetic parameters of the first weight loss were fourthorder, AE = 47 kcaYmol, andA = 2.9 x lo2'-' min-l. For the second weight loss, the parameters were third-order, AE = 32.1 kcaYmol, andA = 3.6 x lo7 min-l. Although third and fourth order elementary reactions are unlikely, the combined effect of simultaneous lower order reactions can give apparent fourth-order reaction kinetics. Apparent reaction rates for the degradation of polymers as high as fifth order have been reported (Friedman, 1968). In a situation as complex as the degradation of a polymer molecule, more than one reaction is to be expected making the apparent reaction order higher than any of the individual reaction orders (Luss and Hutchinson, 1971).
Ind. Eng. Chem. Res., Vol. 33, No. 11, 1994 2605
-4
1
"k %OOOOo
\
0
---
0
ExperimentTGACurve
~ ~ I ~ ) / , , ~ , , ) , , ~ , ,, ~ , , , , ,, , I ,
i
OO
\
1 , , , ~ , ~ , , , 1 , ~ , , 1 , , 1 ~
Conclusions The degradation kinetics of polyaniline base were well represented over most of the weight loss range by second-order reaction kinetics although a shift to lower order kinetics was evident during the last stages of degradation. Sulfonated polyaniline shows two major weight loss regimes that can be approximated as fourthand third-order reaction kinetics. The absence of key degradation products indicates that sulfonated polyaniline has a degradation mechanism distinctly different from emeraldine hydrochloride.
Nomenclature a = heating rate, "Clmin A = pre-exponential factor, min-l A E = apparent activation energy, kcal/mol k = rate constant n = reaction order R = ideal gas constant t = time, min T = temperature, K To = initial temperature, K w = weight loss, mg W = reactant residual weight fraction WO= initial reactant weight fraction W, = residual reactant weight, mg
Literature Cited Anderson, D. A.; Freeman, E. S. The Kinetics of the Thermal Degradation of Polystyrene and Polyethylene. J . Polym. Sci. 1961,54,253-260. Batich, C . D.; Laitinen, H. A.; Zhou, H. C. Chromatic Changes in 1990,137(3),883-885. Polyaniline Films. J . Electrochem. SOC.
Caja, J.; Kaner, R. B.; MacDiarmid, A. J. A Rechargeable Battery employing a Reduced Polyacetylene Anode and a Titanium Disulfide cathode. J. Electrochem. SOC.1984,131 (12),27442750. Doyle, C. D. J. Kinetic Analysis of the Thermogravimetric Data. J. Appl. Polym. Sci. 1961,5, 285-292. Freeman, E. S.;Carroll, B. The Application of Thermoanalytical Techniques to Reaction Kinetics: The Thermogravimetric Evaluation of the Kinetics of the Decomposition of Calcium Oxalate Monohydrate. J. Phys. Chem. 1958,62,394-397. Friedman, H. L. Kinetics of Thermal Degradation of Char Forming Plastics from Thermogravimetry. Application to a Phenolic Plastic. J. Polym. Sci. 1968,6 , 183-195. Green, A. G.; Woodhead, A. E. Aniline-black and Allied Compounds: Part 1.J. Chem. SOC.1910,97,2388-2403. Hagiwara, T.; Yamaura, M.; Iwata, K. Thermal Stability of Polyaniline. Synth. Met. 1988,25,243-252. Hand, R. L.; Nelson, R. F. Anodic Oxidation Pathways of NAlkylaniline. J. Am. Chem. SOC.1974,96 (3),850-860. Kitani, A.; Kaya, M.; Sasaki, K. Performance Study of Aqueous Polyaniline Batteries. J . Electrochem. SOC.1986,133(6),10691073. Kobayashi, T.; Yoneyama, H.; Tamura, H. Polyaniline Film-Coated Electrodes as Electrochromic Display Devices. J. Electroanal. Chem. 1984a,161,419-423. Kobayashi, T.; Yoneyama, H.; Tamura, H. Oxidative Degradation Pathway of Polyaniline Film Electrodes. J. Electroanal. Chem. 1984b,177,293-297. Kost, K. M.; Bartak, D. E. Electrodeposition of Platinum Microparticles into Polyaniline Films with Electrocatalytic Applications. Anal. Chem. 1988,60,2379-2384. LaCroix, J. C.; Diaz, A. F. Electrolyte Effects on the Switching Reaction of Polyaniline. J. Electrochem. SOC.1988,135 (6), 1457-1463. Luss, D.; Hutchinson, P. Lumping of Mixtures with Many Parallel N-th Order Reactions. Chem. Eng. J . 1971,2,172-177. MacCallum, J. R.; Tanner, J. The Kinetics of Thermogravimetry. Eur. Polym. J. 1970,6,1033-1039. MacDiarmid, A. G.; Chiang, J.-C.; Halpern, M.; Huang, W. S.; Krawxzy, J. R.; Mammone, R. L.; Mu, S. L.; Somarasiri, N. L. D. Aqueous Chemistry and Electrochemistry of Polyacetylene and 'Polyaniline': Application to Rechargeable Polym. Prepr. Batteries. (Am. Chem. Soc., Diu. Polym. Chem.) 1984,25,248249. MacDiarmid, A. G.;Mu, S. L.; Somasiri, N. L. D. Electrochemical Characteristics of 'Polyaniline' Cathodes and Anodes in Aqueous Electrolytes. Mol. Cryst. Liq. Cryst. 1985,121,187-190. MacDiarmid, A. G.; Yang, L. S.; Huang, W. S.; Humphrey, B. D. Polyaniline: Electrochemistry and Application to Rechargeable Batteries. Synth. Met. 1987a,18,393-398. MacDiarmid, A. G.; Chiang, J.-C.; Richter, A. F.; Somasiri, L. D.; Epstein, A. J. Polyaniline: Synthesis and Characterization of the Emeraldine Oxidation State by Elemental Analysis. Conducting Polymers; Alcacer, L., Ed.; D. Reidel: Dordrecht, Holland, 198%; pp 105-120. Madorsky, S. L. Rates of Thermal Degradation of Polystyrene and Polyethylene in Vacuum. J . Polym. Sci. 1952,9 (2),133-156. M d e l d , M.; Mu, S. L.; MacDiarmid, A. G. Energy Density, Power Density, and Polarization Studies of the Partially Oxidized ('pdoped') Polyacetylene Cathode. J. Electrochem. SOC.1985,132 (41,838-841. McManus, P. M.; Cushman, R. J.; Yang, S. C. Influence of Oxidation and Protonation on the Electrical Conductivity of Polyaniline. J . Phys. Chem. 1987,91 (3),744-747. Mengoli, G.; Musiani, M. M.; Pletcher, D.; Valcher, S. Studies of ZdZnXflolyaniline Batteries: X=C1 and Br (and X=I). J . Appl. Electrochem. 1987,17,515-524. Oakes, W. G.; Richards, R. B. The Thermal Degradation of Ethylene Polymers. J . Chem. SOC.1949,2929-2935. OBrien, R.N.;Santhanam, K. S. V. Laser Interferometry of Pulsed Galvanostatic Deposition of Polycarbazole. J . Electrochem. SOC. 1985,132 (ll),2613-2616. Osaka, T.; Ogano, S.; Naoi, K. Electrochemical Polymerization of Electroactive Polyaniline in Nonaqueous Solution and Its Application in Rechargeable Lithium Batteries. J . Electrochem. SOC.1989,136,306-309. Ozawa, T. A New Method of Analyzing Thermogravimetric Data. Bull. Chem. SOC.Jpn. 1965,38 (ll), 1881-1886. Paul, E. W.; Ricco, A. J.; Wrighton, M. S. Resistance of Polyaniline Films as a Function of Electrochemical Potential and the
2606 Ind. Eng. Chem. Res., Vol. 33,No. 11,1994 Fabrication of Polyaniline-Based Microelectronic Devices. J. Phys. Chem. 1985,89(8), 1441-1447. Scrosati, B. Electrode and Electrolyte Materials for Polymer-Based Lithium Batteries. J. Electrochem. SOC.1989,136(101,27742782. Stilwell, D. E.; Park, S. M. Electrochemistry of Conductive Polymers: Electrochemical Studies on Polyaniline DegradationProduct Identification and Coulometric Studies. J.Electrochem. SOC.1988,135(lo),2497-2502. Stilwell, D. E.; Park, S. M. Electrochemistry of Conductive Polymers: Degradation Reaction Kinetics of Polyaniline Studied by Rotating Ringdisk Electrode Techniques. J. Electrochem. SOC.1989,136(31,688-698. Traore, M. K.;Stevenson, W. T. K.; McCormick, J.; Dorey, R. C.; Wen, S.; Meyers, D. Thermal Analysis of Polyaniline Part 1. Thermal Degradation of HC1-doped Emeraldine Base. Synth. Met. 1991,40,137-153.
Wei, Y.; Hsueh, K. F. Thermal Analysis of Chemically Synthesized Polyaniline and Effects of Thermal Aging on Conductivity. J . Polym. Sci., Part A: Polym. Chem. 1989,27,4351-4363. Yue, J.; Epstein, A. J. Synthesis of Self-Doped Conducting Polyaniline. J.Am. Chem. SOC.1990,112,2800-2801. Yue, J.; Epstein, A. J.; Zhong, Z.; Gallagher, P. K.; MacDiarmid, A. G. Thermal Stabilities of Polyanilines. Synth. Met. 1991,4143,765-768.
Received for review February 10, 1994 Revised manuscript received J u n e 28, 1994 Accepted July 8,1994@ Abstract published in Advance ACS Abstracts, September 15,1994. @
