Synthesis And Characterization Of Poly (3,4-Ethylenedioxythiophene) Dispersions

Poly(3,4-ethylenedioxythiophene)(PEDOT) is a kind of conductingpolymer with good conductivity, chemical stability, thermal stability andhigh transparency. PEDOT is widely used in a variety of applicationssuch as solar cells, polymer light emitting diodes, etc. In this paper, wefirst give a brief review of synthesis and applications of conductingpolymers. Then the aims of the research on PEDOT in this thesis werepointed out. The main work and conclusions of this paper are showed asfollowing.1, Synthesis and characterization of PEDOT/PSS. Poly(sodiumstyrenesulfate)(PSS) was first synthesized from the monomer, sodiumstyrenesulfonate (SSS) through radical polymerization. Then thePEDOT/PSS was synthesized using PSS as a template. Kinetics ofpolymerization of EDOT was studied by gas chromatography (GC). Itwas found that the polymerization rate of EDOT was faster when thereaction temperature was increased. The reaction rate of EDOT was also increased as the dosages of oxidation were increased and the appropriatedosage of the catalyst was2‰to the monomer. The Iron(III)p-toluenesulfonate and hydrogen peroxide showed more effective inoxidation of EDOT and the polymerization rate was faster when theywere used as the oxidation agent than that of ammonium peroxide. Thepolymerization rate of EDOT decreased when the amount of PSS wasincreased. When PEDOT and PSS mass ratio was1:3, the sheet resistancewas around10KΩ/□. The transparency of PEDOT/PSS film was up to95%, which was measured by UV-vis absorption spectrophotometer(UV).Results from atomic force microscopy (AFM) images showed thatPEDOT and PSS were separated into two different phases. The PEDOTparticles were dispersed in the PSS phases and stacked on the surface ofthe film.2, Synthesis and characterization of PEDOT dispersions withpoly(sodium styrenesulfonate)-g-poly(ethylene glycol) graft copolymer(PSS-MPEG) as the template. The PSS-MPEG was successfully prepared using methoxypolyethylene glycol (MPEG), isophoronediisocyanate (IPDI), hydroxypropyl acrylate (HPA) and sodium styrenesulfonate (SSS) as raw materials. The molecular weight of PSS-MPEGwas about12,000. The particle sizes of PEDOT/PSS-MPEG dispersion,which was around3000nm, were larger than that of PEDOT/PSS. Thesheet resistance of PEDOT/PSS-MPEG film was lower andelectrochemical activity was higher than those of PEDOT/PSS. The lighttransparency of PEDOT/PSS-MPEG film was about95%.3, Synthesis and characterization of PEDOT dispersions usingcopolymers of sodium styrenesulfonate and acrylates as templates. PSScopolymers were prepared from sodium styrenesulfonate and hydroxyl-propyl acrylate or glycidyl methacrylate by radical polymerization. Theparticle sizes of PEDOT/PSS-copolymer dispersions were the same asthat of PEDOT/PSS. Sheet resistances of PEDOT/PSS-copolymer filmswere around30K/□when the molar ratio of SSS to acrylate was（4～6）:1. The transparency to light of the PEDOT/PSS-copolymer films wasup90%, which showed the PEDOT/PSS-copolymer was suitable for the applications in transparent conductive coatings.4, Preparation and characterization of modified PEDOT from blockedaqueous polyurethane (PU) and polyvinyl alcohol (PVA). The sheetresistance of modified PEDOT films with PU was the same as that ofPEDOT/PSS. The water absorption of the PU-modified PEDOT film wasabout7%～15%after the film was heated, which was lower than that ofPEDOT/PSS and the sheet resistance was also reduced. ThePVA-modified PEDOT showed a sheet resistance lower than10K/□.When the amount of PVA used was20%～40%to that of PEDOT/PSS,the sheet resistance of the films was unchanged and the sheet resistancewas increased greatly when the amount of PVA used was more than50%.The addition of PVA improved the properties of PEDOT/PSS dispersionsand made the dispersion to form a film more easily. AFM results showedthat, the addition of PVA made PEDOT particles moved to the surface offilms and phase separation between the PEDOT phase and PSS phasemore apparent.