On the action of ozone on polyaniline

Polyaniline in the emeraldine-base form (PANI-EB) was ozonized in CHCl3 solution. The reaction with O-3 was followed by electronic and FTIR spectroscopy. It is shown that the early stage of O-3 attack on PANI causes the formation of radical cations or polarons in the polymer chain. Ozone treatment also causes formation of nitrite and nitrate groups. The chain degradation reaction seems to be directed preferentially toward the quinoneimine units. Quinoneimine units are already present in PANI-EB but under the oxidizing action of the ozone, additional units are formed. Thus, there is evidence for the formation of a pernigraniline-like structure. However, extensive quinoneimine ring cleavage occurs under the continuing action of ozone. The reactivity of O-3 with PANI-EB appears to be rather low in comparison to the reaction speed with diene rubbers, like for instance, cis-1,4-polyisoprene. (C) 2001 Elsevier Science Ltd. All rights reserved.