The previously found strong dependence of the polymerization enthalpy on the reaction temperature has been rationalized. The
temperature dependence is to be ascribed to the existence of a ‘ceiling temperature’ for the polymerization process of the
pyrrole monomer. The determined ceiling temperature has beenT≊350 K when FeCl3 was used as the oxidizing agent in CH3CN solution. The existence of a ceiling temperature together with its already determined exoenthalpic nature allows to classify
the polymerization reaction as an exoentropic one.
From the dependence of the yield of insoluble polymer on the reaction temperature, the trend of the relative mean numeral
molecular massMn for the different obtained polymers has been determined. Measurements of electrical conductivity on pressed pellets of the
different polymers allowed to establish a correlation between theMn value and the conductivities The dependence of the conductivity on the exposition time to the air allowed to do some essays
on the aging behaviour of the obtained polypyrrole. By making some assumptions, an absolute calorimetric determination of
the value ofMn of polypyrrole was tempted together with that of the related poly-N-vinilpyrrole.