Design,Synthesis And Photophysical Properties Of Luminescent Polyurethane Derivatives

Polyurethane material has the advantages of easy adjustment of chemical structure and good chain flexibility,which has important academic research and application value in photoelectric sensing and other fields.Based on traditional conjugate chromophore polymer luminescent material is generally faced with a difficult problem,which gathered will cause this kind of material of luminescent quenching phenomenon,this phenomenon will cause luminescent material in concentrated solution or solid state luminescence efficiency is greatly reduced,thereby significantly restrict the practical application of this kind of material.How to obtain luminescent materials with excellent photophysical properties in solid state（or aggregate state）through molecular design,and realize its wide application in intelligent fields such as large-area flexible optoelectronic devices and mechanical stimulus response is a great challenge in the research field of polymer luminescent materials.At present,although there are many strategies to improve the aggregation ability of the system,the aggregation in the solution state is mostly passive,which is obtained by using bad solvents as the aggregation driving force.This passive aggregation mode still has many limitations for improving the luminescence performance of the system.First,it is difficult for the chromophores to maximize their luminous behavior in a loosely clustered conformation.Secondly,such aggregation is easy to be disintegrated in practical applications,resulting in greatly reduced luminescence intensity or even quenched.In order to solve these problems,in this paper,the carbamide group（-NH-COO-）repeat unit on the polyurethane main chain is fully utilized to construct the oriented hydrogen bond interaction,which makes the polyurethane molecular chain actively assemble through the self-assembly process without external force,so as to obtain the highly luminescent polyurethane derivatives.The material obtained by this strategy has stable conformation and is not easy to be disintegrated in practical application,which can maximize the optical properties.This paper focuses on the design and synthesis of photoluminescent polyurethane derivatives,and systematically studies the luminescence mechanism,optical response process and response mechanism of these polyurethane derivatives luminescent materials.The research contents are as follows:1.A series of luminescent polyurethane derivatives（PUs）with the properties of aggregation induced luminescence（AIE）and ultra long lifetime phosphorescence at low temperature（LPL）were designed and synthesized.The steady-state photophysics data,time-resolved emission spectroscopy and phosphorescence lifetime decay curve data prove that the entanglement of polyurethane molecular chains in the aggregation state leads to the formation of carbonyl clusters between molecules and within molecules.The spatial conjugation of lone pair electrons in carbonyl clusters is beneficial to the conformation stability of polyurethane molecular chains.The small singlet-triplet energy gap(ΔE_ST)promotes ISC and RISC between singlet and triplet state,and thus prolongating the lifetime of triplet exciton.This is the fundamental cause of both AIE and LPL properties happened in these kinds of materials.Moreover,a PU-based LED with more than 7 seconds afterglow phenomenon at low temperature was obtained.This work provides a new strategy for the design and synthesis of polymer luminescent materials with AIE and LPL properties,and greatly improves the application potential of luminescent polyurethane derivatives in the field of optoelectronics.2.A kind of luminescent polyurethane gel material OUA-gel with supramolecular gel network structure was designed and constructed.Three carboxyl groups in the molecular structure of the aurintricarboxylic acid are used to realize multiple hydrogen bonds interaction and the close-connected polyurethane molecular chains,endowing OUA-gel with highly distorted conformation.So that different fluorescent changes are available according to different degrees of mechanical stimulation,which can be easily distinguished by the naked eye.The internal mechanism is that the molecular conformation of OUA-gel transforms from amorphous to crystalline state slowly under mechanical action.This work can help us to understand the internal relationship between local conformation and whole luminescence properties of gel materials,deepening the understanding of multi-color luminescence mechanism of soft materials,promoting the molecular design process of advanced intelligent materials.3.A series of deep blue light emitting materials OUHDI,OUHMDI and OUTDI were designed and synthesized.The results of fluorescence spectra,transmission electron microscopy images,FT-IR spectra and rheology data showed that polyurethane molecular chains were self-assembled to a nanotube-like structure through hydrogen bond interaction.The interaction between discrete carbonyl units generates a variety of oxygen clusters aggregates,which is favorable for high luminescent performance.Besides,the simultaneously introducing of heteroatoms can be beneficial to enhance the photophysical properties of polyurethane derivatives in the aggregated state,which makes the polyurethane derivatives exhibit enhanced mechanical properties and deep blue emission in the self-assembled gel state.Deep blue emission polyurethane gel material was successfully applied to the preparation of viscous coating,transparent film and fluorescent model.These physically crosslinked luminescent polyurethane gels are highly processable and have broad development prospects in practical applications such as large-area luminescent coatings,advanced composites,solid-state lighting and thermal sensing.This work provides a new strategy of designing deep blue luminescent polyurethane derivative materials,which proves the practical application potential of polyurethane derivative luminescent materials for high quality display device.4.A series of red,green and blue fluorescent polyurethane derivatives were designed and synthesized by controlling the conjugate length of chromophore in the main chain of polyurethane and systematically adjusting the energy gap of luminescent polyurethane derivatives.Powder X ray diffraction,FT-IR spectrum,fluorescence spectrum and SEM images data prove that the inter-molecular and intra-molecular hydrogen bonding interaction are the driven force for the self-assembled gelation of polyurethane,making the flexible polyurethane chains intertwined and extension.Thus,an extended network strcture can be obtained by increasing the molecular chain entanglement and reducing the distance between the chromophores.This network with holes can cause F?rster resonance energy transfer between chromophores.A white light emitting diode（CIE:0.35,0.33）was successfully prepared by precisely controlling the stoichiometry of OUB,OUG and OUR according to the principle of three primary colors and the dynamic characteristics of physical crosslinked gel.This work will combine the excellent physical properties of unconventional luminescent material and excellent viscoelasticity of gel material.This series of luminous polyurethane materials show good solution processability,thixotropy,soft,easy to coating and tunable optical properties,which proves it can be a new generation of intelligent material,having a wide range of application in different fields like Light-Emitting Diodes,large area coating,flexible equipment.5.A series of fluorescent polyurethane derivatives PUDA、PUH and PUD were designed and synthesized.PUDA、PUH and PUD showed high selectivity and sensitivity for2,4,6-trinitrophenylphenol（TNP）,and this process could be quickly recognized by naked eyes.Fluorescence spectra,ultraviolet absorption spectra and cyclic voltammetry data showed that the static and dynamic quenching processes are coexisted in the fluorescence quenching process.It is also proved that the fluorescence quenching response mechanism of these luminescent polyurethane derivatives for TNP is an effective combination of internalization filter effect,F?rster resonance energy transferand photoinduced electron transfer.In addition,a simple test paper for visual detection of TNP was prepared using fluorescent polyurethane derivatives.The minimum detection limit of the test paper was as low as 10^-10M,0.229 ag/cm².This work provides a simple,low-cost and efficient polymer luminescent material for TNP detection of explosives,which is conducive to promoting the practical application of luminescent polyurethane derivatives in the field of rapid detection.