Multi-Sterically Hindered Pyrene-Based Blue Light Material And Its Flexible Light-Emitting Polymer Composite Film

With the rapid development of plastic electronics,flexible materials for preparing plastic electronics have been widely studied.Compared with traditional inorganic semiconductors,organic polymer semiconductor materials have lower Young’s modulus,which makes them have great application potential in stretchable electronic devices.However,with the development of science and technology,electronic devices made from organic polymer semiconductor materials with small form variables can no longer meet the increasingly complex application range.The composite materials formed by fluorescent molecules and polymers not only meet the performance of devices but also have large shape variables.Moreover,this composite method can effectively inhibit the aggregation of molecules and achieve the effect of luminescence enhancement,which provides a new solution for the sustainable development of plastic electronics.We designed and synthesized four blue fluorescent materials(PF-Py,DPF-Py,TPF-Py and FPF-Py)and investigated the photophysical behavior of these four blue molecules in different aggregation states and the composite films formed by polymers.The research contents are as follows:First,Four kinds of pyrene blocking blue light materials(PF-Py,DPF-Py,TPF-Py and FPF-Py)were designed and synthesized based on Friedel-Crafts reaction.Nanocrystals of PF-Py,DFF-Py and FPF-Py were prepared by reprecipitation method.The quantum efficiencies of PF-Py,DFF-Py and FPF-Py were measured in solution,spin-coated film and nanocrystalline state respectively.The results show that the PLQY of these three molecules in nanocrystalline state is 189%,110% and 18%higher than that of spin-coated film respectively,indicating that they can effectively inhibit the aggregation quenching between molecules in crystalline state.Thus,the PLQY is improved,and it is proved that PF-Py,DFF-Py and FPF-Py have the properties of crystallization induced luminescence enhancement.Then,Four kinds of composite films were prepared by blending the powders and nanocrystals of PF-Py and DPF-Py into polydimethylsiloxane(PDMS),which are as follows: PF-Py powder and PDMS composite film,PF-Py nanocrystalline and PDMS composite film,DPF-Py powder and PDMS composite film,DPF-Py nanocrystalline and PDMS composite film,DPF-Py powder and PDMS composite film,DPF-Py nanocrystalline and PDMS composite film and the morphology,photophysical and mechanical properties of the composite films were investigated.Results show that the doping concentration of 5 wt% PF-Py crystal composite membrane morphology most smooth uniform,compared with the unstretched intrinsic composite film,90% of the tensile deformation of the composite film fluorescence intensity increased to 30 times on average,compared with the bending,stretching can inhibit the aggregation degree of molecular clusters in composite membrane increase its luminous enhancement and fluorescence quantum efficiency.According to the mechanical properties test of PF-Py nanocrystalline composite film,compared with the Young’s modulus of pure PDMS film without nanocrystalline doping(2.03 Mpa),the Young’s modulus of the composite film with 10 wt% nanocrystalline doping content is increased to 2.25 Mpa,indicating that nanocrystalline doping can improve the Young’s modulus of the composite film.Finally,Four kinds of thin films were prepared by compounding the powders and nanocrystallines of PF-Py and DPF-Py with water-soluble polyvinyl alcohol(PVA),and the preparation process and photophysical behavior of these four thin films under different stresses were studied.The study shows that the morphology of the composite film is the most flat and uniform when the PF-Py nanocrystal content is 3 wt% and 39°C.Under this condition,we successfully prepared a large area of composite film and realized the patterning of the film through the origami process.In terms of the fluorescence properties of the composite films,compared with the intrinsic composite films,the fluorescence intensity of the four composite films increased at different ranges under 30%tensile deformation,which once again proved that the aggregation degree of molecular clusters could be inhibited by tensile deformation,resulting in luminescence enhancement.In summary,four kinds of polypyrene blocking blue light materials were synthesized by FriedelCrafts reaction in this paper,and amorphous and nanocrystalline pyrene based materials were combined with silicon based polymer and stream polymer respectively to form films.The film forming process of composite films and the effect of pyrene molecular cluster aggregation in composite films on their fluorescence intensity were explored.This study provides a new way to improve the luminescence intensity of molecules.