Blue Light-emitting Organic Nanopolyfluorene:Nanosynthesis And Characterization

Fluorene-based polymers,as promising blue light emitting materials,have been investigated extensively in the past decades owing to their easy modification,high fluorescent efficiency,and deep-blue light emitting.However,various morphologies,green band emission and low mobility blocks commercial application.How to improve the performance of fluorene-based materials comprehensively for electric pump oganic laser is still a problem.Our group have proposed a grid-based nanopolymer strategy that possess both advantages of nanomaterials and polymer to solve the problem.Therefore,we have designed a series of nanomonomers and corresponding nanopolymers.Structre-property relationship is investigated by NMR,MALDI-TOF-MS and spectrum.The details are listed following:Firstly,in order to study the grid effects,T-shaped oligofluorene is used as steric hindrance to obtain H-shaped nanomonomer with the yield up to 85%.The corresponding nanopolymer PH is synthesized via Yamamoto reaction.Importantly,nanopolymer PH exhibits good solubility in commom solvents and high thermal stability with the decomposition temperature of 420?.However,the nanopolymer exhibits poor spectral stability with ca.40%enhancement in intensities of green band emission after annealing 1 hour at 180? in air,and ca.100%enhancement for 4 hours in the same environment.Moreover,significant change is observed in morphology after annealing.Besides,poor performance in terms of amplified spontaneous emission?ASE?properties and PLED devices maybe result from the wide PDI and the residual metal catalyst in the nanopolymer.Secondly,for the propose of improving spectral stability of nanopolymers,a nano-grid was synthesized via A₁B₁ type Friedel-Carfts reaction of L-shaepd synthon with the yield of 72%and its corresponding?-interruped nanopolymer PGTh is synthesized.We find that conformational isomerism exists in monomer and there is little influnces in opticalphysics and electrochemical properties among the isomers and their corresponding nanopolymers.Rations of R_g and R_h in various environments are larger than 2.0,indicating that nanopolymre PGTh is an extended rigid chain.In addition,PGTh exihibts both better thermal stability and spectral stability than that of nanopolymer PH.Green band emission is not observed after annealing 2 hours at 180? in air.Finally,another grid was synthesized via A₂+B₂ type Friedel-Carfts reaction of U-shaepd synthon with the yield of 45%and its corresponding?-nanopolymer PGCz is synthesized.A series of studies indicate that PGCz shows good stability in terms of themal performance,electrochemical property,spectrum and morphology,only ca.32%enhancemet in intensities of green band emission after annealing 8 hours at 180? in air.Besides,ASE properties are also observed from PGCz.Therefore,grid-based nanopolymers may become new generation photoelectric materials that possess excellent stability and performance.