Synthesis and Properties of Naphthalimide Fluorescent Dye and Covalent Fluorescent Polyurethane Emulsion

Abstract

The reactive fluorescent dye 4- methoxy- N-(2- hydroxy- 1- hydroxymethylethyl) naphthalimide(MHHNA) was first synthesized by imidization and substitution reactions using 4-bromo-1,8-naphthalic anhydride,2- amino- 1,3- propanediol, and sodium methoxide as initial materials. A series of covalent fluorescent polyurethane(PU)(PU-MHHNA) emulsions were then fabricated using MHHNA as the chain extender through a phase inverse self-emulsification process. The chemical structure of the synthesized fluorescent dyes and the properties of PU-MHHNA emulsions and their latex films were characterized by1 H nuclear magnetic resonance(1H NMR) spectroscopy,13 C nuclear magnetic resonance(13C NMR) spectroscopy, Fourier transform infrared(FTIR) spectroscopy, elemental analysis, ultraviolet- visible(UV- Vis) absorption spectroscopy,fluorescent spectroscopy, particle size analysis, and xenon arc aging measurements. The fluorescent quantum yields of MHHNA and PU-MHHNA were 0.73 and 0.92, respectively. The amount of MHHNA had no obvious influence on the colloidal properties of the PU-MHHNA emulsions. The maximum wavelength(λmax) of the UVVis absorption spectra was 360.6 nm, and fluorescent spectroscopy analysis indicated that the maximum excitation wavelength(λex) and maximum emission wavelength(λem) of PU-MHHNA in acetone were 362 and435 nm, respectively. In addition, the fluorescence intensity of PU- MHHNA decreased with increasing temperature. The light fastness and solvent fastness of the PU-MHHNA film were much better than those of the non-covalent fluorescent polyurethane(PU/MBNA) film.