Photo-stability of yellow-green emitting 1,8-naphthalimides containing built-in s-triazine UV absorber and HALS fragments and their acrylonitrile copolymers

Two novel 1,8-naphthalimide dyes, containing active fragments of both 2-(2-hydroxyphenyl)-1,3,5-triazine UV absorber and 2,2,6,6-tetramethylpiperidine radical scavenger as well as a polymerisable allyl group, were designed as multifunctional yellow-green emitting fluorophores capable simultaneously of chemically fluorescent dyeing and photo-stabilisation of polymers. Their basic photo-physical characteristics have been determined and are discussed. It was shown that combination of different structural units in the 1,8-naphthalimide molecule does not result in their interaction through intramolecular fluorescence quenching due to an electronic energy transfer. The ability of the combined dyes to copolymerise with acrylonitrile was demonstrated as polyacrylonitriles stable to solvents and with an intense colour and fluorescence were obtained. Photo-degradation of the new fluorophores and their influence on the photo-stability of the coloured copolymers have been studied and compared to other similar fluorescent dyes, not containing either UV absorber or hindered amine fragment in their molecules as well as not containing both of them. Novel fluorophores showed the best photo-stability in both solution and polymer. A significant photo-stabilising effect towards photo-destruction of polyacrylonitrile was found, which might be caused by a possible “synergism” of two stabiliser fragments differing in their action.