Synthesis and characterization of a novel waterborne stilbene-based polyurethane fluorescent brightener

A novel waterborne stilbene-based polyurethane fluorescent brightener dispersion WPU-VBL was synthesized by incorporating chemically disodium 4,4′-bis[(4-anilino-6-hydroxyethylamino-1,3,5-triazin-2-yl)amino]stilbene-2,2′-disulphonate (VBL) into the polyurethane chain using isophorone diisocyanate, poly(propylene glycol) and 2,2-dimethylol propionic acid. The structure of WPU-VBL was confirmed by means of Fourier transform infrared spectroscopy. The UV–vis absorption analysis showed a hypsochromic shift of 16 nm when VBL was blocked into polyurethane chain. Number average molecular weight of 2.1 × 104, molecular weight distribution of 2.1 and average latex particle size of about 70 nm for WPU-VBL were determined based on the analysis of gel permeation chromatography and laser particle size analyzer. It was found that the fluorescence intensity of WPU-VBL was prominently enhanced because of the micro-circumstance of VBL and the fluorescence of WPU-VBL was very stable.