Controlling the kinetics of photo-oxidation processes of PPV derivatives: application in radiation sensors

Full text: Since the discovery of semiconducting properties of conjugated polymers, their electronic properties have attracted attention due to their promising applications as active layers in several optoelectronic devices. However, low durability still remains as a challenge in technological applications. Taking into account that the barriers to oxygen and moisture rely on the encapsulation to prevent degradation, and that radicals formed during polymer processing can propagate in presence of small amounts of oxygen, it is important to find alternative ways to improve the photo-stability of conjugated polymers, without affecting the electronic properties of these materials. On the other hand, the change of color induced by radiation has been recently explored in the development of light dosimeters since a relationship between the light intensity that reaches the sample and the color change can be established. In this sense, we control the photo degradation of a poly(p-phenylene vinylene) based polymers (BDMO-PPV, MDMO-PPV and MEH-PPV) adding a radical scavenger or a radical initiator and the kinetics parameters (rate constant, rate law and half time) of these reactions were determined. Photoluminescence, UV-Vis absorption, FTIR and ¹H NMR spectroscopes revealed that the incorporating small amounts of radical scavenger or radical initiator is an efficient way to control the rates of the photo-oxidation reactions. The determination of the kinetics parameters apart from the pure physical chemical interest will help to improve the performance and lifetime of optoelectronic devices and adjust the dose-response of the radiation sensors. (author)