Reversible photodimerisation of omega-anthrylpolystyrenes

The preparation of polystyrene with controlled molar masses and narrow dispersity endcapped with an anthrylmethyl ether group, as well as the study of their photophysical properties, are described. Under irradiation at 336 nm dimerisation of the polystyrene chains is observed. This process results from the formation of a symmetrical head-to-tail photodimer between two anthryl end groups. When irradiated at lower wavelength (lambda = 228 nm), the original omega-anthrylpolystyrene chains are quantitatively restored. These dimerisation/dissociation cycles can be conducted more than ten times without any detectable degradation of the photosensitive polymer. The fluorescence emission quantum yield and fluorescence lifetime of the omega-anthryl moieties and the quantum yield of the dimerisation and of the reverse process have been measured.