IN-SITU DOPING POLYMERIZATION OF PYRROLE WITH SULFONIC-ACID AS A DOPANT

doping polymerization of pyrrole in the presence of sulfonic acid as a dopant have been investigated. It was found that sulfonic acids which have a good solvating ability, e.g. beta-butylnaphthalene sulfonic ac id (BNSA), beta-naphthalene sulfonic acid (NSA) and p-dodecylbenzene s ulfonic acid (DBSA), render PPy soluble in m-cresol, while sulfonic ac ids, e.g. camphor sulfonic acid (CSA) and p-methylbenzene sulfonic aci d (MBSA), cannot. Therefore, it was proposed that a good solvating abi lity of sulfonic acid induces the solubility of PPy. The UV-Vis and ES R spectra indicated that the charge carriers in PPy doped with NSA, BN SA, CSA, DBSA, p-hydroxylbenzene sulfonic acid (HBSA) and 5-sulfo-isop hthalic acid (SIA) are polarons and bipolarons, while only bipolarons serve as charge carriers in PPy doped with alizarin red acid (ARA) and 8-hydroxy-7-iodo-5-quinoline sulfonic acid (QSA). The nature of sulfo nic acid also has influence on morphology and thermostability of the r esulting PPy. It was found that the polymerization medium significantl y influences the solubility and conductivity of PPy. The in situ dopin g polymerization of pyrrole in organic solvent such as CHCl3, CH3NO2 o r THF gave soluble but nonconductive PPy, compared with insoluble but conductive (sigma = 18 S/cm) PPy prepared in water. (C) 1998 Elsevier Science S.A. All rights reserved.