Synthesis And Properties Of Coumarin Derivatives AFC-terminated Fluorescent Cationic Waterborne Polyurethane With High Solid Content

Waterborne polyurethanes are multi-functional environmentally friendly materials which have attracted a great deal of attention. However, the drying rate of WPUs is much slower compared to the solvent-based polyurethanes with the same solid content because of the high latent heat of evaporation of water. Therefore, the drying time and energy consumption of WPUs increased, which was difficult to meet the requirement of time efficiency and economic benefit. Hence, the research now is mainly focused on the preparation of the WPUs with high solid content. At present, in most of the previous researches were predominant to synthesize the anionic WPUs. No surprisingly, there are not a significant number of papers available in the open literature that describe the synthesis of cationic high solid content WPU.In this paper, we have adopted a new concept of soft segment(SS) and hard segment(HS) to design a new route of synthesis high solid content waterborne polyurethane. A series of high solid and high stability cationic waterborne polyurethanes with high solid content were designed and synthesized by introducing different cationic hydrophilic chain segments(polyoxyethylene alkyl amine, PAE) into the soft segment. The properties of emulsion and film was measured by infrared spectroscopy(FTIR), laser particle size analyzer, tensile mechanics, thermogravimetry analyses(TGA), water absorption and contact angle analyses. It was found that the quantity of ethylene oxide(EO) in PAE is 10, n(PAE): n(POL7112) is 1:9, and n(NCO)/n(OH) is 1.2, the cationic waterborne polyurethane can be synthesized that the solid content is 51.28%, which has controllable bimodal particle size distribution(PSD). With addition of PAE, the breaking elongation of film increased remarkably, the hydrophilicity is reinforced, the thermal stability is obviously improved and the tensile strength has a slight downtrend. The particle size decreases with the increment of EO content in PAE molecule, and the emulsion stability reinforced.In order to further investigate the specific application and the influence of stereohindrance, temperature and solvatochromic of fluorescence. Following the same process, a novel anionic AFC-based waterborne polyurethane was synthesized by importing the fluorescent agent 7-amino-4-(trifluoromethyl) coumarin(AFC) into the polyurethane chains. Structure of the CWPU-AFC was confirmed by Fourier transform infrared spectroscopy(FTIR) and UV-visible absorption spectroscopy. Number average molecular weight and average emulsion particle size for CWPU-AFC were also determined. It was found that the fluorescence intensity of CWPU-AFC decreased with the increasing temperature and was enhanced compared with that of AFC. The improved thermal stability of CWPU-AFC could be attributed to the incorporation of benzopyrone units in the preformed urethane groups. Furthermore, the fluorescence of CWPU-AFC emulsion was very stable for long-term storage.