THERMAL-PROPERTIES OF POLYANILINE AND POLY(ANILINE-CO-O-ETHYLANILINE)

Block copolymers of aniline (r(1) < 1) and ethylaniline (r(2) > 1) can readily be formed by acid-catalyzed oxidation. These copolymers have enhanced solubility in common solvents, compared to polyaniline. For e xample, while a 47 mol % o-ethylaniline copolymer is 2-7 times more so luble in ethanol, methanol, and acetone than polyaniline, the solubili ty of the copolymer in tetrahydrofuran increases by more than 20 times . Thermal effects on the properties of polyaniline and poly(aniline-co -o-ethylaniline) in their emeraldine base forms have been studied by m eans of thermogravimetric analysis (TGA), differential scanning calori metry (DSC), electron paramagnetic resonance (EPR), four-probe conduct ivity, UV-vis, and FT-IR spectroscopies. Upon heating, the number of f ree electrons in the polymer, as determined by EPR, increases by up to 10 times. An irreversible exothermic transition was observed by DSC, which is believed to be an indication of cross-linking. The electron-d onating character of the ethyl group appears to help stabilize the int ermediates during the cross-linking reaction. Complete characterizatio n of the copolymer is given.