Intramolecular exciplex formation and non-radiative quenching in alternating copolymer of 2-vinylnaphthalene and 2-(dimethylamino)ethyl methacrylate in dilute solution

Alternating and random copolymers of 2-vinylnaphthalene and 2-(dimethylamino)ethyl methacrylate have been synthesized. The random copolymers showed both excimer and exciplex emissions in 1,4-dioxane, the former of which became more important with increasing naphthyl content in the copolymer. For the alternating copolymer, in contrast, an exciplex emission but no discernible excimer emission was observed. This indicates negligible interaction between naphthyl chromophores and complex formation between neighbouring naphthyl and 2-(dimethylamino)ethyl groups. However, additional quenching still occurs in the alternating copolymer, which may be attributed to the interaction of two amino groups with the excited naphthalene. Introduction of unreactive monomers into the copolymer and separation of the dimethylamino groups from the polymer main chain are found to be effective in reducing the extra quenching.