Preparation Of Poly(vinyl Alcohol)/Polyurethane Blend Nanofiber Mats And Their Fluorescent Modification

In this study, poly(vinyl alcohol) (PVA)/polyurethane (PU) blend nanofiber mats were prepared through duel-jet electrospinning process (DJESP) and an orthogonal experimental design (L9(3)³) was used for optimizing the electrospinning parameters. Meantime, several inorganic fluorescent compounds were synthesized by Pechini method, and one organic fluorescent compound was synthesized by Knoevenagel condensation reaction. In order to achieve the modified PVA/PU blend nanofiber mats with fluorescent properties, those fluorescent compounds were doped into the spinning solution, respectively, and fluorescent mats were also prepared by DJESP.Exact studies included as follows: The influence of tip-to-collector distance (TCD), voltage and tip-to-tip distance (TTD) on the morphology of electrospun fiber during the process of duel-jet electrospinning was investigated by an orthogonal experimental design (L9(3)3). In the selected optimum electrospinning conditions, the morphology, thermal stability, mechanical and hydrophilic properties of PVA/PU blend nanofiber mats were tested. And the morphology, luminescence property and fluorescence lifetime of synthesized inorganic fluorescent nanoparticles were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), single-photon emission fluorescence spectra and luminescence decay curve. Besides, one synthesized organic fluorescent dye was characterized by 1H NMR, FT-IR, UV-Vis absorption spectra, single-photon emission fluorescence spectra and reflectance spectra. Both inorganic fluorescent nanoparticles and organic fluorescent dye were doped into the electrospinning solution, respectively, to prepare fluorescent compound/PVA/PU blend nanofiber mats by DJESP. Then the morphology and luminescence property of the fluorescent nanofiber mats were investigated.Result showed that:(1) In the system of preparation of PVA/PU blend nanofiber mats by duel-jet electrospinning, the main parameters affecting the fiber diameter was TCD, while the main parameters affecting the fiber diameter distribution was TTD. And the optimum electrospinning conditions were TCD of 20 cm, voltage of 18 kV and TTD of 4 cm. The decomposition temperature of blend nanofiber mats was a little higher than that of pure PVA and PU nanofibers. The PVA/PU blend nanofiber mats were more flexible than pure PVA and stronger than pure PU. And hydrophilicity of the blend nanofiber mats was also very well. In a manner of speaking, the PVA/PU blend nanofiber mats embodied the advantages of both PVA and PU nanofiber.(2) The phosphors of Eu₆WO₁₂, La₆W_xMo_1-xO₁₂:Eu³⁺ and LaBO₃:RE³⁺ nano-particles were prepared by the Pechini method. XRD, SEM, fluorescence spectrometer and decay curves were used to characterize the phosphor samples. The excitation and emission spectra showed obvious fluorescence effect although the size of LaBO₃:Ce³⁺ and LaBO₃:Tb³⁺ were not very evenly. When the phosphor was mixed into spinning solutions, the fluorescent nanofiber mats of inorganic compound/PVA/PU could be prepared by DJESP. Although the incorporation of inorganic phosphors had a little affected on the morphology of the electrospun fibers, the fluorescence emission spectra of blend nanofiber mats were basically same as that of inorganic phosphors, which confirmed that the PVA/PU blend nanofiber mats could be fluorescence modified by the phosphors of Eu₆WO₁₂, La₆W_xMo_1-xO₁₂:Eu³⁺ and LaBO₃:RE³⁺ nano-particles.(3) The organic fluorescent dye was successfully synthesized and characterized. It could be efficiently excited by near UV light (458nm) and exhibits an intense red luminescence at 595nm. When DHEASPBr-C4 was mixed into spinning solutions, the fluorescent nanofiber mats of DHEASPBr-C4/PVA/PU could be prepared by DJESP. Although the incorporation of DHEASPBr-C4 had a little affected on the morphology of the electrospun fibers, the fluorescence effect of blend nanofiber mats were very well, which confirmed that the PVA/PU blend nanofiber mats could be fluorescence modified by DHEASPBr-C4.