Kinetic studies of the photo-degradation of poly(arylene vinylenes)

The kinetics of the degradation of a homologous series of poly(phenylene vinylenes) in which the phenylene units of the PPV structure are systematically substituted by naphthyl and anthyrl units is presented. Degradation is monitored according to the decay of the long wavelength absorption maximum upon illumination with UV radiation. Compared to toluene solution, the photo-degradation is seen to be accelerated in chloroform solution. All decays are fitted with first order kinetics. It is found that all substitutions improve the stability of the vinylene polymers against decay. In particular the highly electro-negative naphthyl group serves to drastically increase the stability due to electron depletion across the vinyl bond. The decay rate is shown to correlate well with the variation of the electronic properties of the backbone and with the reduction of vinylene bond strength as measured using Raman spectroscopy.