Study On Thermal Activation Delayed Fluorescence And Room Temperature Phosphorescence Properties Of Diphenylsulfone/Benzophenone Derivative Waterborne

Thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)are the most promising and effective methods for efficiently utilizing triplet excitons in the field of organic light emitting diodes(OLEDs).They can break through the theoretical limits of quantum yields of traditional fluorescent OLED devices and achieve higher energy utilization.At present,the mainstream design idea is to realize the thermal activation delayed fluorescence by constructing a twisted donor-acceptor structure.The molecular synthesis route of this structure is complicated,and it is often necessary to use a noble metal(such as palladium)catalyst,which is difficult to popularize and apply.The performance of small molecule luminescent materials is limited by the aggregate structure and is more toxic.Compared with small molecules,polymer materials have better mechanical properties,thermodynamic properties and processing properties,and they have practical application value.Waterborne polyurethane is an environmentally friendly polymer material with high polarity,good temperature tolerance and easy adjustment of monomer components.It can suppress the thermal quenching phenomenon of luminescent molecules by adjusting the ratio of soft segment and hard segment of waterborne polyurethane.Therefore,it is of great significance to explore waterborne polyurethanes with thermally activated delayed fluorescence and room temperature phosphorescence properties via luminescent molecules as functional monomers.1.Five diphenyl sulfone derivative diols and two benzophenone derivative diols were designed and synthesized:bis-(4-(2-hydroxyethyl)(methyl)amino)diphenyl sulfone(BNS),bis-(4-(2-hydroxyethyloxy))diphenyl sulfone(BOS),bis-(4-(2-hydroxyethylthio))diphenyl sulfone(BSS),(4-(N,N-Dihydroxyethyl)-amino)phenyl-phenylsulfone(NS),4-(N,N-dihydroxyethyl)-amino-4'-methoxydiphenyl sulfone(NOS),4-(N,N-dihydroxyethyl)-amino-4'-methoxybenzophenone(ONP)and 4-(N,N-dihydroxyethyl)-amino group-4'-cyanobenzophenone(CNP).Their structures were verified by nuclear magnetic resonance spectroscopy and infrared spectroscopy;UV-Vis absorption spectrum shows that the derivative molecules have strong CT structure compared with the unsubstituted diphenyl sulfone and benzophenone;the steady-state fluorescence emission spectrum and transient photoluminescence decay curves show that they only have weak fluorescence emission at room temperature,so it needs to be incorporated into waterborne polyurethane to restrain thermal quenching of triplet excitons.2.BNS,BOS,BSS,NS and NOS this five diphenyl sulfone derivative diols were incorporated into waterborne polyurethane covalently to synthesize a series of waterborne polyurethanes(P1,P2,P3,P4 and P5)with thermally activated delayed fluorescence properties.Among them,P1,P4 and P5 shows efficient thermally activated delayed fluorescence.P1,P2 and P3 all exhibits higher ?EST(9 kcal/mol).However,since P1 has an efficient singlet-triplet vibrational energy level coupling(P2 and P3 do not),even with a large ?EST,P1 can emit thermally activated delayed fluorescence.P4 and P5 show sufficient energy level coupling while having a small?EST,RIC and RISC processes are easy to occur,so most excitons are radiated from the TADF pathway.In summary,thermally activated delayed fluorescence in waterborne polyurethanes can be realized via serving charge-t:ransfer states as a mediate bridge.3.In order to find out the effect of different additional groups in D-A system on room temperature phosphorescence properties,ONP and CNP were used as chain extenders incorporated into waterborne polyurethanes.It was found that when additional functional group is methoxy,the system has good phosphorescence emission performance(?=276 ms,?=0.75);when additional functional group is cyano,the phosphorescence emission becomes very weak,and more sensitive to concentration.