Eliminate Conjugated Molecular Intramolecular Rotation To Obtain Ultra Long Room Temperature Phosphorescent Polymers

Twisted donor-acceptor molecules,even doped into rigid and polar polymers,are rarely able to exhibit ultra-long organic room temperature phosphorescence,which is recognized to be caused by the fact that the internal rotation unit is very unfavorable for ultra-long RTP.If the internal rotation of N-arylcarbazole derivatives can be chemically eliminated in advance,it will undoubtedly be beneficial to the stabilization of the triplet state by the polymer matrix,and will develop a new type of ultra-long RTP material not limited to hydrogen-bonded polymer groups.In this paper,N-(obromophenyl)carbazole was used to generate [3,2,1-jk] carbazole by intramolecular coupling.The formed indolocarbazole is used as a doping molecule to achieve ultralong room temperature phosphorescent polymers.1.A series of novel [3,2,1-jk] carbazole derivatives with peripheral functionalization were doped into rigid plastic PMMA to emit ultra-long and bright RTP afterglow.The RTP lifetime is far more than 2 s,which is basically the longest lifetime in doped PMMA polymers.According to low temperature experiments and quantum chemical calculations,eliminating intramolecular rotation and expanding π system have a unique and positive effect on RTP enhancement.2.The current ODRTP research system uses rigid and polar polymers as the doping matrix.Rigid polystyrene(PS)is rarely used and studied because of its nonpolarity,so styrene-isoprene-styrene block polymer(SIS)should not be an effective matrix for ODRTP due to its non-polar and elastic characteristics.The cyano-containing fused heterocyclic molecules that have pre-eliminated intramolecular rotation exhibit excellent RTP properties after doping SIS,and the RTP lifetime reaches 1.14 s.At the same time,the mechanism of SIS promoting RTP was discussed.By studying the photophysical properties of rubber EPDM,non-polar rigid polymer PS and ductile plastic HIPS with PS as continuous phase,it was found that the stress concentration effect of phase interface was stable for triplet excitons.3.In order to further study the promoting effect of phase interface on RTP,[3,2,1-jk] carbazole derivatives were doped into rigid polar polymer PMMA and thermoplastic elastomer SIS by increasing the phase interface.After doping into PMMA/ SIS polymer,it emits brighter afterglow than PMMA,and its lifetime reaches 2.89 s.By using photometer illumination measurement,it is found that both the initial brightness after removing the excitation light source and the brightness decay rate are better than the single polymer.Uncovering the phase interface of nonpolar heterogeneous polymer systems can effectively inhibit the triplet thermal inactivation and at least evoke the ultra-long ODRTP of [3,2,1-jk] carbazole derivatives.In this paper,the problem of non-radiative decay caused by severe internal rotation is solved from the molecular structure,and an organic doped molecular system with extended π system plane is provided,which provides an extremely favorable prerequisite for various polymer matrices to effectively stabilize the triplet state.The use of doped thermoplastic elastomer SIS and thermoplastic rigid plastic PMMA and mixed doping has expanded the problems that the RTP properties of ultra-long RTP polymers cannot be sustained and stable and the mechanical properties are single.