Synthesis And Characterization Of Iridium Containing Liquid Crystalline Polymers

In the text,nematic monomers M1 and M2,cholesteric monomer M3 are synthesized;iridium complexes L were synthesized with Ir3+ as the center,2-(4-Methylphenyl)pyridine as the first ligand and acrylic acid as the second ligand;Three series of iridium contained liquid crystalline luminescent polymers was prepared by the reaction,in which mesogenic monomer and iridium complexes were grafted to the main chain of PMHS.Moreover,the iridium contained liquid crystal luminescent polymers are novel.As an important component of Organic Light-Emitting Diode(OLEDs),liquid crystal luminescent materials play an important role in obtaining high efficiency OLEDs.According to spin statistics theory,the ratio of singlet exciton and triplet exciton is 1:3.In the process of luminescence,the fluorescence material only uses the singlet exciton radiation attenuation luminescence and its internal quantum efficiency is only 25%.In order to make full use of singlet exciton and triplet exciton luminescence and improve the luminous efficiency of materials,metal based liquid crystal luminescent materials have been favored by researchers.The iridium complex has high luminous efficiency,strong phosphorescence emission at room temperature and can adjust the wavelength of luminescence by adjusting the ligand structure,so that the color of the luminescent device can cover the whole visible region.The iridium luminescent core is introduced into liquid crystal polymers and the concentration quenching phenomenon of materials in the process of luminescence is inhibited to some extent by using the special three-dimensional structure of iridium complex.The liquid crystal polymers is provided a high efficient light source.The liquid crystal luminescent polymers synthesized in this paper combine the strong luminescence properties of iridium complexes with the processing properties of polymer materials,which have the advantages of easy processing and easy realization of large area display.The structures and properties of the obtained liquid crystalline monomers,iridium complex and the iridium contained liquid crystal luminescent polymers are investigated by FT-IR spectroscopy,1H-NMR spectroscopy,differential scanning calorimetry(DSC),thermogravimetric analyses(TGA),polarizing optical microscopy(POM),and X ray measurement.Their structure-property relationships are discussed in detail:(1)M1 and M2 exhibit marble texture of the nematic phase during the heating and cooling cycles.M3 displays oil-streak texture of the cholesteric phase during the heating and cooling cycles.(2)P1 and P2 series of the polymers showed nematic marble textures.P3 series of the polymers showed cholesteric grandjean textures.For polymers P1,P2 and P3 series,when the concentration of iridium complexes unit increased from 0 mol%to 1.2 mol%,Tg of P1,P2 and P3 series increase,but T1 decrease.Pi,P2 and P3 series display wide mesophase temperature ranges(?T>100?).?T values decreased with increasing the content of iridium complex,The weight loss of all the polymers took place at the temperature above 200?.(3)The UV absorption band under 370 nm of P1,P2 and P3 series that iridium containing liquid crystal polymer belong to the ligand spin allowed singlet ?-?*transition;the weak absorption peaks in the range of 370 nm to 480 nm should be attributed to the spin allowed 1MLCT(metal-to-ligand charge transfer);the weak absorption peaks in the range of 480 nm to 600 nm belong to the triplet states spin orbit coupling enhanced 3?-?*transition and the spin forbidden 3MLCT,this part is absorption characteristics of phosphorescent materials,strongly spin orbit coupling of the center metal iridium makes forbidden transition allowed.(4)Polymers P1,P2 and P3 series can emit characteristic phosphorescence of Ir3+.when Ir3+ ion content increases the luminescent intensity of the polymers gradually increases accordingly.At Ir3+(mol%)=1.2%,polymers still did not show concentration quenching.Polymers Pi,P2 and P3 luminescent intensity decreased monotonically with the increasing temperature in the studied range.This is because the increase of temperature greatly increases the probability of the occurrence of nonradiative transition and causes the intensity of light to weaken.When the temperature continues to rise,the nonradiative transition will dominate.At this time,the phenomenon of temperature quenching will occur.