Design And Investigation Of Ultralong Room Temperature Phosphorescent Polymer Materials Constructed By Hydrogen Bonds

Polymer materials have attracted increasing attention in the field of organic room temperature phosphorescence(ORTP)because they are not only easy to process,low cost,and flexible,but also have polymer chain lengths that are easily entangled and can act as rigid matrices like lattices to suppress the molecular vibration and the rotation of phosphors,which is beneficial to the emission of phosphorescence.At present,most of the long-lived ORTP materials are based on organic small molecular crystals,and their single crystal growth conditions are harsh.Some reported polymeric room-temperature phosphorescent materials also have the shortcomings of short lifetime and high sensitivity to water,oxygen and temperature.In most reported RTP materials,hydrogen bonding is a powerful way to improve performance because the network structure formed by hydrogen bonding can greatly confine the vibration of phosphorescent molecules and reduce nonradiative deactivation.Based on this,two series of copolymers containing phosphorescence emitting groups and hydrogen bond building units were designed and prepared,and their phosphorescent light-emitting properties and color-tunable properties were studied.1.Four different ratios of phosphorescent monomer carbazole-dibenzofuran(CDF)and copolymers P1～P4 containing quadruple hydrogen bond monomer(H-H-UPy)were designed and synthesized.Structural characterization of monomers and polymers were identified by nuclear magnetic resonance spectroscopy,time-of-flight mass spectrometry and Fourier transform infrared spectroscopy,while the actual molar percentages of phosphorescent moieties in the polymers were calculated from the elemental analysis data.The photophysical properties of polymers P1～P4 were systematically investigated.Due to the lowest content of CDF in P1,it was best dispersed in the multiple hydrogen bond network formed by UPy,so it can fix the phosphorescence unit well,and its phosphorescence lifetime reached the longest of 2.16 s.Although P4 has the highest CDF content,it still achieved a phosphorescence lifetime of 1.99 s due to the formation of H aggregates.In addition,it was found by theoretical calculation that the high triplet state of H-H-UPy can play the role of the host,transfer energy to the guest CDF,and promote the intersystem crossing process from singlet state to triplet state,which is beneficial to phosphorescence emission.Finally,due to the formation of super-strong intermolecular hydrogen bonds between the UPy groups,the phosphorescence of the polymer can be stable for a long time in water;and interestingly,a part of the phosphor can still be fixed at a high temperature of 100 °C,that is,it can still display phosphorescence emission.2.Based on the excellent properties of the aforementioned ultralong phosphorescent polymer materials,the phosphorescent luminescence color was further extended,and an orange phosphorescent luminescent unit was introduced in order to obtain a polymer room-temperature phosphorescent material with multicolor tunable and white light emissions.First,two copolymers of CDF,4-bromo-1,8-naphthalimide(Br Np A)and N-isopropylacrylamide(NIPAM)with different feeding ratios were designed and synthesized.The obtained polymer films exhibited phosphorescence lifetimes of 1.86 s and 1.62 s,respectively,and decent phosphorescence quantum efficiency.Notably,at different excitation wavelengths,color-tunable fluorescence emission was obtained,including cold white light.After turning off the UV excitation,a multi-color tunable afterglow with excitation-dependent and time-dependent properties was produced,including warm white afterglow,and the CIE coordinates were(0.31,0.37).In addition,standard white phosphorescence with CIE coordinates(0.34,0.33)was obtained after the polymer film was immersed in hydrofluoric acid.The introduced F atom promoted the ISC and enhanced the blue delay fluorescence,which combined the yellow phosphorescence of Br Np A and produced standard white afterglows.The dual-mode multicolor emission properties of this copolymer offer promising applications for advanced anti-counterfeiting applications.