Thermo-oxidative stability of a conjugated polymer by chemiluminescence

Conjugated polymers based on 1,4-phenylenevinylene units are very promising materials for applications as light-emitting diodes. A major requirement i s their stability at elevated temperatures of operation. The thermo-oxidati ve behaviour of a soluble poly(1,4-phenylenevinylene) derivative, poly[2,5- bis(2-ethylhexyloxy)-1,4-phenylene vinylene], was investigated by using che miluminescence and UV-Vis absorption spectroscopy. Extremely sensitive chem iluminescence is successfully applied since even minor chemical changes cou ld lead to a considerable loss of photo- and electro-optical properties. Va rious degradation processes are described as a function of time and tempera ture and their influences on functional properties are discussed. The inves tigated material does not show sufficient thermo-oxidative stability within the temperature range of intended use in contact with air. For industrial application, direct contact with oxygen during processing and operation has to be avoided. (C) 2000 Elsevier Science Ltd. All rights reserved.