A series of reactive fluorescent dyes were successfully synthesized and their structure was proven by IR spectra, NMR spectra, elemental analysis, and mass spectra. The fluorescence performance 6-amino-2(-3-phenyl-propyl)-benzo[de]isoquinoline-1,3-dione and 2-benzyl-6-hydroxy-benzo[de]isoquinoline-1,3-dione appears at around 276 and 437.4 nm, respectively, and their quantum yields are 0.662 and 0.562, respectively. It is important to indicate that the fluorescence performance is better for 6-amino-2(-3-phenyl-propyl)-benzo[de]isoquinoline-1,3-dione than for as a result of more electron donating groups linked to the 6-amino-2 (-3-phenyl-propyl)-benzo[de]isoquinoline- 1,3-dione molecule. These fluorescent dyes further react with toluene diisocyanate and other additives to form fluorescent dye based polyurethane (PU) ionomer molecules, and their structures are demonstracted by IR spectra. In aqueous solution, the fluorescence performance appears to be better for 6-amino-2(-3-phenyl-propyl)-benzo[de]isoquinoline-1,3-dione based PU ionomer than for 6-amino-2-phenyl-ethyl-benzo[de]isoquinoline-1,3-dione based PU ionomer. For the fluorescent dye based PU ionomer molecule system, the number-average particle sizes of the fluorescent dye based PU ionomer molecules in water increase with increasing concentration of the fluorescent dye, as a result of the increased free volume of the ionomer molecule. This may be the result of increased intermolecular interactions between ionomer- molecules themselves. (c) 2005 Wiley Periodicals, Inc.