Poly(p-phenylene vinylene) (PPV) and its derivatives have recently received considerable attention in the field of electroactive organic materials chiefly because of their potential to replace the standard inorganic semi-conducting materials in light-emitting devices. Currently efforts are being made to reduce the carbonyl and hydroxyl defects in these materials which act as quenching sites for the injected charge. Thus, the understanding of the origin of these defects in PPV is extremely important in order to improve its electroluminescence efficiency. These defects are found to appear during the thermal conversion of PPV from its precursor, In this paper we have studied the thermal elimination reaction sequence in a PPV precursor using thermogravimetry and mass spectrometry and the observed results have been associated with standard reaction mechanisms to explain the formation of the aforementioned defects.