Thermal stabiligy of luminescent conducting polymers

The thermal stability of luminescent conducting polymers as PLED materials and intelligent optical fiber additives directly influences their service lifetime. The thermal stability and degradation kinetics of a luminescent conducting polymer, poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), are investigated in this paper. The lifetime is predicted based on the thermal properties. The DTG curves indicate a double-stage decomposition process in the nitrogen atmosphere, and a multi-stage decomposition process in the air atmosphere. The apparent activation energy values of MEH-PPV are higher in the nitrogen than under air. Activation energies are slightly increasable and approximately stable in nitrogen for the initial mass loss, while the activation energy changes differently with the percentage of 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.