Photo-oxidation of polymers

Photo-oxidation oxidation reactions that are triggered by light. The reaction rate of oxidation depends among other parameters, important from the light absorption of the oxidized species from.

Mechanism

A photon excites the electron of the molecule, so that it is raised to a higher electronic level. In this excited state is generally a low probability that a spin flip of the electron occurs, that is, the excited molecule comes into the triplet state.

Is now oxygen in close proximity ( overlap of the molecular orbitals ) to the molecule exists, the energy can be transferred, ie the molecule is in the ground state and the oxygen in the excited state. It creates highly reactive singlet oxygen, which can undergo oxidation reaction with the molecule.

Since oxygen has a triplet ground state ( which is extremely rare), the energy transfer only works from the triplet state of the molecule by Dexter energy transfer, as only then the spin conservation is given.