We have studied the elimination reaction of n-alkylsulfinyl-PPV and -OC1C10-PPV precursor polymers toward conjugated materials with in situ FT-IR and UV-vis spectroscopy. The temperature at which the elimination reaction starts in nitrogen flow is as low as 65 and 70degreesC, for the PPV and OC1C10-PPV precursor polymers, respectively. Under vacuum conditions, the elimination temperature shifts even to lower temperatures. After elimination, a certain amount of elimination products, which are set free during the elimination reaction, remain in the OC1C10-PPV polymer matrix, while in pure PPV, the elimination products are ejected more extremely from the polymer matrix. After completion of the elimination reaction, an absorption maximum of 416 and 490 nm (T = 150degreesC) is obtained for the corresponding PPV and OC1C10-PPV, respectively. This effective conjugation length decreases again, by degradation of the conjugated system, around 330degreesC for the PPV polymer and around 230degreesC for the OC1C10-PPV polymer. From nonisothermal experiments in which the elimination reactions is studied in situ with FT-IR spectroscopy, we are able to determine an experimental activation energy (EA) for the conversion reaction, which has a value that is in good agreement with the EA that was obtained by theoretical modeling (104.6 kJ/mol or 25 kcal/mol).