Conjugated Polymers With Tunble Emission Color Synthesized Via Oxidation Polymerization

Due to their great potential in the fields of polymer light-emitting diods (PLEDs),conjugated polymers have attracted more and more attentions. The synthesis routines of conjugated polymers usually include oxidative polymerization(electrochemical and chemical routes),catalytic condensation as well as catalyzed coupling methods.However,oxidative polymerization,compared with other methods,is the most convenient method to obtain conjugated polymers.Conjugated polymers,which have both the wide bandgap units and narrow bandgap units in their backbone,can be used as the emission layer in PLEDs,and become one of the research focus in the field of PLEDS. As well known,poly(3,4-ethylene dioxythiophene)(PEDOT) is a narrow bandgap polymer with outstanding chemical and electrochemical stability. In the former part of this paper,various contents of 3,4-ethylene dioxythiophene(EDOT) units is introduced into the wide bandgap conjugated polymers,such as polypyrene,polyphenylene,polyfluorene, polycarbazole and polytriphenylamine,via oxidation polymerization,and five series of conjugated copolymers with various emission colors in visable light have been obtained.FTIR and ~1H NMR spectra are used to characterize the polymer structures.Elemental analysis results show that the content of EDOT units in copolymers increase as the feed of EDOT in monomer mixturte increase.The PL spectra maximum of poly(pyrene-co-EDOT) are influenced by polymerization methods dramaticly,while affected by monomer feed ratio slightly.The bluegreen-emission color of copolymers obtained via electrochemical routine present their PL maximum around 440 nm,and the green-emission color of copolymers obtained via chemical routine exhibit their PL maximum around 510 nm.The PL maximum of poly(benzene-co-EDOT) obtained via chemical or electrochemical methods redshift to long wavelength as the feed of EDOT in monomer mixturte increase.Poly(fluorene-co-EDOT) and poly(carbazole-co-EDOT) can only be obatined via chemical oxidation polymerization.Though poly(triphenylamine-co-EDOT) can be synthesized via both chemical and electrochemical oxidation,all the products present poor solubility.As the EDOT contents increase in the monomer feed,the fluorescence color of three types of copolymer redshift from blue to green,and the PL maximum of poly(fluorene-co-EDOT),poly(carbazole-co-EDOT) and poly(triphenylamine-co-EDOT) redshift from 419,430 and 433 nm to 514,502 and 530 nm,respectively.Cyclic voltammetry results show that these polymers have a reversible redox behavior.Thermogravimetric analysis showed that all above copolymers have a higher thermal decomposition temperature than PEDOT.Wide-angle X-ray diffraction show that these copolymers are non-crystalline.Usually,polythiophene is theα-αcoupling conjugated polymer,and have a very wide range of application.The later part of the work of this paper is the synthesis of 2,5-diphenyl-thiophene(DPT) firstly,and then the corresponding polymer(PDPT) has been prepared vai electrochemical method.FT-IR result shows that PDPT hasβ-βlinkages between thiophene units,PL spectrum presents that PDPT emiss blue fluorescence, electrochemical tests show that PDPT has reverisble and stable redox behavior,SEM result shows that PDPT film has smooth surface.In addition,alkyl,alkoxy,carboxyl and sulfonic acid-substitutedβ-βpolythiophene derivatives,even the corresponding polypyrrole derivatives,may be prepared by using this method,thus extending the structures,performance and the applications of conjugated polymers.