전기화학적으로 합성된 폴리피롤의 열안전성

최재순; 김경림; 김동영; 이준영; 김정엽

Polymer(Korea), Vol.21, No.4, 525-531, July, 1997

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전기화학적으로 합성된 폴리피롤의 열안전성

Thermal Stability of Electrochemically Synthesized Polypyrrole

최재순, 김경림, 김동영, 이준영, 김정엽

초록

여러가지 도핑제를 사용하여 전기화학적으로 폴리피롤을 합성하고 전기전도도 측정과 열안정성 실험을 행하였다. 도핑제에 따라서 4 S/cm로부터 130 S/cm까리 넓은 범위의 전기전도도를 나타내었으며 열안정성도 도핑제의 종류에 크게 영향을 받았다. 열분석 결과, 확연한 질량감소가 관찰되는 온도가 200 ℃에서 400 ℃ 사이로 도핑제에 따라 달랐으며 이러한 질량감소가 도핑제의 열분해에 의한 것임을 확인하였다. 열분석 실험에서 열분해 온도가 높았던 안트라퀴논-2-술폰산, 안트라퀴논-2,6-술폰간나트륨염 및 구리프탈로시아닌나트륨염을 전해질로 사용하여 얻은 폴리피롤은 200 ℃와 250 ℃에서 열처리할 때 전기전도도의 감소가 아주 작았으나 분해온도가 낮은 전해질을 사용하여 얻은 시료들은 전기전도도의 감소가 매우 큼을 알 수 있었으며 이로부터 전기전도도의 감소는 도핑제의 열분해와 직접적인 관계가 있음을 알 수 있었다. UV-VIS 분석 결과, 전기전도도의 열안정성이 나쁜 시료들은 열처리할 때 480nm 근처의 흡수밴드가 청색이동을 하였는데 이는 도핑제의 열분해에 의하여 폴리피롤 중의 공액이중 결합길이의 감소에 의한 것으로 판단된다.

Polypyrrole (PPy) films synthesized electrochemically with various dopants were investigated in terms of thermal stability and electrical conductivity at high temperatures. The conductivity of PPy films ranged from 4 S/cm to 130 S/cm depending greatly on the kinds of dopants used. A considerable weight loss was observed in a temperature range of 200∼400 ℃ on thermogravimetric analysis (TGA). PPy doped with a thermally stable dopant such as anthraquinone-2-sulfonate ion lost its weight slightly at 250 ℃ on TGA but the conductivity changed little on isothermal heating at 200 ℃ as well as at 250 ℃. But a PPy film doped with a thermally less stable dopant showed a large decay in the conductivity as well as the weight loss on heating at 200 ℃. In the case of thermally unstable samples, a blue shift of the absorption band at 480 nm was observed possibly due to a reduction in π-conjugation length on the thermal degradation of the polymers or the dopants.

Keywords:polypyrrole;electrical conductivity;thermally stable dopant;electrochemical polymerization

[References]

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[1] "Handbook of Conducting Polymers," ed. b T.J. Skothiem, Marcel Dekker Inc. (1986)

[2] Stedt HM, Polymer, 29, 296 (1988)

[3] Wang Y, Rubner MF, Synth. Met., 41, 1103 (1991)

[4] Thielemont JC, Planche MF, Petrescu C, Bouvier JM, Bidan G, Synth. Met., 59, 81 (1993)

[5] Burford RP, Moss BK, J. Intell. Mat. Sys. Struct., 5, 749 (1994)

[6] Neoh KG, Kang ET, Tan KL, J. Appl. Polym. Sci., 43, 573 (1991)

[7] Samuelson LA, Druy MA, Macromolecules, 19, 824 (1986)

[8] Ennis BC, Trung VT, Synth. Met., 59, 387 (1993)

[9] Min KS, Kim JK, Rhee HW, Kim CY, Polym.(Korea), 17(3), 301 (1993)

[10] Montgomery HC, J. Appl. Phys., 42, 2971 (1971)

[11] Qian R, Qiu J, Polym. J., 19, 157 (1987)

[12] Ko JM, Rhee HW, Kim CY, Makromol. Chem. Macromol. Symp., 33, 353 (1990)

[13] Thieblemont JC, Brun A, Marty J, Planche MF, Calo P, Polymer, 36(8), 1605 (1995)

[14] Bredas JL, Scott JC, Yakushi K, Street GB, Phys. Rev., B, Condens. Matter, 30, 1023 (1984)

[15] Patil AO, Heeger AJ, Wudl F, Chem. Rev., 88, 183 (1988)

[16] Kaufman JH, Colaneri N, Scott JC, Street GB, Phys. Rev. Lett., 53, 1005 (1984)

[17] Nishikawa O, Kato H, J. Chem. Phys., 85, 6758 (1986)

[18] Lee JY, Kim DY, Song KT, Kim SY, Kim CY, ANTEC'96, 1422 (1996)

[19] Lee JY, Kim DY, Song KT, Kim SY, Kim CY, Mol. Cryst. Liq. Cryst., 280, 135 (1996)

[20] Coles BR, Caplin AD, "The Electronic Structures of Solids," Edward Anold Ltd., London (1976)

[21] Omar MA, "Elementary Solid State Physics," Addison Welsely, Reading (1975)