A novel 1,8-naphthalimide green fluorescent dye and its corresponding intrinsically fluorescent polyurethane latexes

A novel green fluorescent dye, 4-hexylamino-N-(2-hydroxy-1-hydroxymethylethyl)-1,8-naphthalimide (AHHNA), was designed and synthesized, and then used as a chain extender to prepare a series of intrinsically green fluorescent polyurethane (PU) latexes. The chemical structure of AHHNA and the properties of the fluorescent PU latexes and their films were characterized. It was found that the UV-Vis and the fluorescent spectra of the PUs remained fairly consistent with AHHNA, and the fluorescence emitting capacity of 1,8-naphthalimide group was enhanced by covalently bonding AHHNA onto the PU chain. The amount of AHHNA used in the latex preparation had no obvious effect on the latex colloid properties including particle size, poly index, and zeta potential. Results showed that the color difference (Delta E) and the extraction rate (R (e)) of the intrinsically fluorescent PU latex film were 5.72% and 3.1%, respectively, while the Delta E and R (e) of the extrinsically fluorescent PU latex film were 8.31% and 84.7%, respectively, indicating that the light fastness and the solvent fastness of the intrinsically fluorescent PU latex film were much better than those of the extrinsically fluorescent PU latex film.