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C: static capacitor measured at 120 Hz; 

ESR: equivalent series resistance measured at 100 kHz; 

DF: dissipation factor measured at 120 Hz. 

The results summarized in Tables 1 and 2 clearly dem› onstrated that the capacitor prepared by the conventional oxidative polymerization method (as in Comparative Example B) based on the conventional composition (EDOT/ Fe(OTs )$_{3}$ ) had failed totally after been heated at 240° C. for 38 minutes, having a DF value (2.92) that had already much over 0.12 that is acceptable upper limit value of DF for a commercial solid capacitor. All the capacitors prepared by the newly invented cationic chain-growth polymerization method (Examples 5-8) from the composition of the inven› tion (BEDOT plus acid catalyst) had all survived from the thermal treatment at 240° C. for 38 minutes. The results have further indicated that the performance of the capacitors in Examples 5-7 had actually already downgraded to some extents (though still appeared within the acceptable range), showing decreased capacitances together with increased ESR and DF values. Clearly, only the capacitor in Example 8 (with the addition of both polymerization retardant and polymer binder as the functional components) could com› pletely overcome such thermal heating treatment, without suffering any degradation. Actually, the DF value of Example 8 had been unexpectedly and significantly reduced further from 0.016 to 0.011. The results herein clearly confirmed that the composition and polymerization method of this invention can render the solid capacitors with much higher thermal stability than the conventional composition and method. The results further indicated that best perfor› mance can be achieved when both polymerization retardant and polymer binder are used as the functional components of this invention. 

## Examples 9-11. Withstanding or Breakdown Voltage Test I 

An anode aluminum foil having an Al$_{2}$ 0 3 dielectric layer formed at an electrochemical forming voltage of 50 V and 6 a cathode aluminum foil of high surface area prepared by an electrochemical erosion were wounded together with an interposed separator to form a solid electrolytic capacitor element, as conventionally designed for a capacitor with a rated voltage of 35 V and a rated capacitance of 220 µF. After the electrochemical reforming treatment in an organic acid solution to repair the damaged dielectric layer, the capacitor element was dipped for 10 minutes in a compo› sition solution containing monomer (BEDOT; 1.5 M) and various acid catalyst (as listed in Table 3; 0.15 equiv) together with the functional components of both polymer› ization retardant (ether, 2 equiv) and polymer binder (poly [styrene-co-(methyl methacrylate)]; PS-PMMA; 0.2 equiv). Then, the polymerization was performed by heating the 

dipped capacitor element at the elevated temperatures rang› ing from 60° C. to 190° C. for 30 min to drive the polymerization to completion. After the preparation, the resultant capacitors were all subjected to aging treatments to reduce their leakage currents to below the value of -154 µA (i.e., -0.02 CV). The capacitors were then subjected to withstanding or breakdown voltage test, respectively, by raising the applied voltage gradually until the breakdown of the electrolyte had occurred or until 48 V (the voltage slightly below the forming voltage of the anodic Al foil) was reached. The results of the withstanding or breakdown voltage for the respective electrolytes are summarized in Table 3. 

A wounded aluminum capacitor, as prepared by the same method in Examples 8-11, was dipped with a monomer solution of 3,4-ethylenedioxythiophene (EDOT; 30 wt %) and then with an oxidant solution of iron(III) tosylate (Fe(OTs)$_{3}$ ; 30 wt%; 2.5 equiv) for 10 minutes, respectively. Then, the polymerization was performed by heating the dipped capacitor element at the elevated temperatures rang› ing from 60° C. to 190° C. for 30 min to drive the polymerization to completion. After the preparation, the resultant capacitor was all subjected to aging treatments to reduce its leakage current to -154 µA. The capacitors were then subjected to the same withstanding or breakdown voltage test, as in Examples 9-11, by raising the applied voltage gradually until the breakdown of the electrolyte. The breakdown voltage is listed in Table 3. 

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0 BEDOT: 2-bromo-3,4-ethylenedioxythiophene; 

EDOT: 3,4-ethylenedioxythiophene; 

DBSA: dedecylbenzenesulfonic acid; 

DNNDSA: dinonylnaphthalenedisulfonic acid; 

PSS: poly(styrenesulfonic acid); 

Fe(OTs)s: iron(III) tosylate. 

The results summarized in Table 3 clearly indicated that the solid capacitor containing the conventional solid elec- 

## Comparative Example C 

