| Polyfluorene materials have been widely studied as star molecules of organic broad-gap luminescence.However,the sp~3 carbon at 9-position of fluorene is very active and tends to be oxidized in light,heating,electrification and humid environment,thus forming the ketone defect,one of the three green bands.In the early stage,our research group has designed and synthesized conjugated nanopolygrid PGDPF that is resistant to heat oxygen and water oxygen,which provides a new solution to the dilemma faced by the stability of polyfluorene materials.However,in the study of photooxidation,PGDPF shows poor photooxidation stability.This paper conducted a series of exploration and verification on the abnormal phenomenon of PGDPF in photooxidation stability.In addition,the stability of photooxidation and thermal oxidation of trapezoidal polygridarenes,trapezoidal gridarenes and their precursor synthons were investigated to verify the effect of lattice effect and polymerization effect on the stability.In chapter 1,we firstly synthesized Br-free trapezoidal grid GDPF and Br-free type I-Shape,and carried out a series of basic characterization of these two molecules,which prepared for the subsequent study of grid effect and polymerization effect.Secondly,we re-explored the PGDPF photooxidation experiment under the same conditions as those given in the past,and found that the experiment was not repeatable.Finally,photooxidation of PGDPF was explored from three aspects of light intensity,film thickness and ozone.The results showed that ozonated water was the main factor leading to PGDPF photooxidation.In chapter 2,because the ozone experiment in the previous chapter introduced both ozone and light intensity,and the ultraviolet power in the ozone experiment is much higher than that used to explore the effect of light intensity,it was not convincing enough to ignore the influence of light intensity on the experiment.In this chapter,we first refined the ozone experiment.The photooxidation of PGDPF was investigated from three aspects of low light and ozone,no light and ozone and high light and oxygen by controlling single variable.The results show that ozone is the main cause of PGDPF photooxidation,and ultraviolet light is only the means of ozone generation.Secondly,in order to explore the effects of grid effect and polymerization effect on photooxidation,we carried out photooxidation experiments on GDPF,I-Shape,U-Shape and PGDPF under UV-cleaner.The results show that grid effect can improve the photooxidation resistance of materials,but polymerization effect can not improve the photooxidation stability of materials.Finally,we put PGDPF,PODPF and PCz DPF,which have been published with good stability of the same type,into the UV cleaner for photooxidation experiment.The results show that compared with the world’s leading level of PCz DPF,the photooxidation resistance of PGDPF needs to be improved,but compared with PODPF,the photooxidation resistance of PGDPF was significantly improved.In Chapter 3,we compare the thermo-oxygen stability of GDPF,I-Shape,U-Shape and PGDPF from molecular,time and temperature factors.The results show that the thermo-oxygen stability of the trapezoidal grid monomer GDPF is better than that of I-Shape and U-Shape,but weaker than that of the trapezoidal polygird PGDPF,which indicates that both grid effect and polymerization effect can improve the thermo-oxygen stability of the material.In conclusion,we explored the main factors causing PGDPF photooxidation,revealed the aggregation effect and cyclic effect on the stability,and implemented a comprehensive investigation on the photooxidation and thermal oxidation stability of linear molecules,grid molecules.In this regard,this work provided a new strategy to improve the opto-electronic property of the fluorene-based wide-bandgap semiconductors... |
PDF Full Text Request