Preparation of waterborne polyurethane with outstanding fluorescence properties and programmable emission intensity

The hard segment content and hydrophilic group content of a fluorescent waterborne polyurethane (FWPU) were used to optimize the polymer structure which can influence the fluorescence properties. The synthesis of FWPU was based on 2,2′-((4-([3,3′:6′,2″-terpyridine]-4′-yl)phenyl)azanediyl)diethanol (TPPDA) as fluorophore. The structure of FWPU was characterized using Fourier transform infrared and 1H NMR spectroscopies, and the polymer molecular weight and polydispersity were measured using gel permeation chromatography. The relationship between fluorescence properties and FWPU structure was studied using luminescence spectrometry. Compared to TPPDA, the maximum emission wavelength of FWPU showed a hypsochromic shift, and the fluorescence emission intensity and quantum yield of FWPU were increased obviously. Moreover, increasing the hard segment content led to an enhancement of the fluorescence lifetime of FWPU, and to the fluorescence intensity increasing at first and then decreasing. The fluorescence emission intensity and quantum yield of FWPU were increased nearly 11 and 7 times, respectively, compared to TPPDA when the hard segment content was 65%. With an increase of hydrophilic group content, the fluorescence emission intensity of FWPU increased. The fluorescence emission intensity of FWPU exhibited a response to pH, which facilitated its employment as a fluorescence probe. FWPU with excellent solid fluorescence is very suitable for processing into optical devices, with increasing hard segment content and hydrophilic group content both enhancing the solid fluorescence emission intensity of FWPU. © 2016 Society of Chemical Industry