SINGLET OXYGEN AS A REACTIVE INTERMEDIATE IN THE PHOTODEGRADATION OF AN ELECTROLUMINESCENT POLYMER

Singlet molecular oxygen (a(1) Delta g) is shown to be a reactive inte rmediate in the photoinduced oxidative decomposition of the electrolum inescent material is(5,6-dihydrocholestanoxy)-1,4-phenylenevinylene) [ BCHA-PPV] in both liquid solutions and solid films. Upon irradiation o f this polymer in CS2, singlet oxygen is produced by energy transfer f rom the BCHA-PPV triplet state to ground state oxygen with a quantum y ield of similar to 0.025. Singlet oxygen reacts with BCHA-PPV, resulti ng in extensive chain scission of the macromolecule. The reaction with singlet oxygen is unique to the polymer; the monomeric analog of this system, stilbene, does not appreciably react with singlet oxygen. Pol ymer degradation is proposed to proceed via addition of singlet oxygen in a (pi)2 + (pi)2 cycloaddition reaction to the double bond that con nects phenylene groups in the macromolecule.