Synthesis and fluorescent investigations of VBL-based waterborne polyurethane dye

Fluorescent brightening agent VBL-based waterborne polyurethane dye (VBL–WPU) was synthesized by incorporation of VBL into waterborne polyurethane chains. The expected structure of polymeric fluorescent brightening agent was confirmed by FT-IR and UV–vis spectra. The molecular weight, average particle sizes and the contents of VBL segments in VBL–WPU were investigated. This polymeric dye exhibited intriguing optical behaviors. The absorption and emission maxima of VBL–WPU showed obviously hypsochromic shift in comparison with those of VBL. The fluorescence intensity of the polymer was prominently enhanced comparing with VBL because of the changes of micro-circumstance of VBL. Furthermore, the fluorescence of VBL–WPU was not sensitive to hydroquinone quencher.