Room-temperature Polymer-based Long Persistent Materials

In recent years,pure organic phosphorescent materials that do not contain precious metals have attracted more and more attention because of their unique luminous behavior.Compared with inorganic phosphorescence,the realization conditions of organic phosphorescence are usually more stringent.With the unremitting efforts of many researchers,there are many strategies to promote the effective emission of organic phosphorescence.In this thesis,the main strategy is to introduce phosphor into polymer matrix and combine the host guest doping strategy to develop a series of pure organic phosphor materials which can emit stably under ambient conditions,and their mechanism and application are explored.The main content of this thesis is divided into the following three parts:In the first part,three cyanuric chloride phosphors(CzDCIT,BiCzDT and TCzT)modified with different numbers of carbazolyl groups were synthesized.Several characterization techniques were employed to reveal distinct crystal forms of CzDCIT,BiCzDT and TCzT.The single crystal diffraction of CzDCIT and BiCzDT showed not only different crystal packing modes,but also the formation of internal H-aggregation.These three phosphor powders exhibited dual emissions of blue fluorescence and yellow phosphorescence at room temperature,with luminescence lifetimes of 0.16-0.34s.Theoretical calculations indicated that different numbers of effective intersystem crossing channels between CzDCIT,BiCzDT or TCzT were responsible for the luminescence lifetimes.After doping the phosphors into the polymer matrix,they exhibited good persistent phosphorescence and high recoverability in multiple compression-grinding cycles.In the second part,dibenzothiophene(DBT)was selected as the host,and N,N,N',N'-tetramethylbenzidine(TMB)and melamine(MA)were used as the guest,polyvinyl alcohol was used as the matrix to prepare a series of polymer-based long-lived persistent films in a simple way.It was found that the addition of guest improved the phosphorescence emission behavior of these films to some extent,which was due to the n??~*transition constructed by nitrogen atoms in the guest promoted the intersystem crossing and the fixation and protection provided by polymer matrix to triplet excitons.At last,according to the water solubility of these films,a kind of stimulus response phosphorescent material with good recoverability was developed.In the third part,DBT,TMB and DBF were selected as the host,and some common organic solvents such as THF,DMF,Methanol and Ethanol were used as the guest,PVA as the matrix to prepare a series of polymer films.Phosphorescence enhancement or quenching occurred in films of DBT system and DBF system after doping with organic solvents,and fluorescence and phosphorescence colors of TMB system films changed from blue to green after doping with organic solvents.