Structure and Fluorescent Performance of Waterborne Polyurethane-Acrylate Based on a Carbazole Derivative

A purple fluorescent monomer, 2-[3-(9-ethylcarbazole)ureido]ethyl methacrylate (CUMA), was synthesized from 3-amino-9-ethylcarbazole and 2-isocyanatoethyl methacrylate. A series of fluorescent waterborne polyurethane-acrylate emulsions (PCUMA-PUA) were obtained by the step-growth addition polymerization method. In this method, a polyurethane prepolymer was terminated with C=C first, then reacted with CUMA by free radical polymerization. It was demonstrated that the hydrophobic component in the amphiphilic PCUMA-PUA is preferentially located on both ends of the copolymer. The molecular structures of the monomer and the copolymer were confirmed with Fourier transform infrared (FTIR) and UV–Vis absorption spectra. It was observed that the fluorescence intensity of the PCUMA-PUA copolymer is higher than CUMA at the same concentration of fluorophores in aqueous solutions. It was also observed that when the mass fraction of CUMA was higher than 2 wt%, self-quenching behavior became evident. The new composite films were ascertained to have an increased thermal stability with increasing CUMA content.