The thermal conversion of dialkylsulfonium polyelectrolyte precursor polymers Ib-e to poly(p-arylene vinylene)s was studied by direct pyrolysis mass spectrometry in order to elucidate the mechanism of the sulfonium elimination reaction. The temperature dependence of the single ion currents of the four more abundant volatile products was correlated with the structural changes introduced in the arylene moiety of the polyelectrolytes and with the counterion nature. Experimental results suggest that the elimination reactions in the solid state proceed through an E2 mechanism.