Thermal degradation kinetics and lifetime prediction of a luminescent conducting polymer

The thermal stability, degradation kinetics and lifetime-prediction of a luminescent conducting polymer, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), are investigated. The derivative thermogravimetry curves indicate a double-stage decomposition process in a nitrogen atmosphere, and a multi-stage decomposition process in an air atmosphere. The apparent activation energy values of MEH-PPV are higher in nitrogen than in air. Activation energies slightly increase and are then approximately stable in nitrogen for the initial mass loss, while the activation energy changes differently with the percentage mass loss in air. The activation energy decreases for the initial mass loss and increases with mass loss when the mass loss is above 30%; beyond 70% it decreases again. The lifetime of MEH-PPV decreases dramatically from 106 min to 0.03 min as the temperature increases from 25°C to 300°C in air. The lifetime is longer in nitrogen than in air and decreases from 1014 min to 2.34 min with increasing the temperature from 25°C to 300°C in nitrogen. These lifetime parameters indicate that the service/process temperature has a strong influence on the luminescence of MEH-PPV. The maximum absorption and wavelength at maximum absorption of MEH-PPV decrease with increasing temperature in the visible region.