Fundamental Study Of Lignosulfonic Acid As A Dispersant And Dopant Of Poly(3,4-ethylenedioxythiophene)

It is of important theoretical significance and pratical value to prepare water dispersed conductive composites using lignosulfonic acid(LS), which was drawn from the pulping black liquor, as a carrier, and to clarify the basic principles in it. Based on the poly(3,4-ethylenedioxythiophene)/lignosulfonic acid(PEDOT/LS) complexes, studys were done about the preparation conditions, influencing factors and mechanism of the system. Also, the micro structure and application prospect were studied. The main research progress and achievements are as follows:3,4-ethylenedioxythiophene(EDOT) was successfully polymerized chemically in LS aqueous solution with oxidant Na2S2O8, resulting in a PEDOT/LS conductive aqueous dispersion. We found that the optimal oxidative polymerization conditions were: the weight ratio of LS to EODT was 2:1, the molar ratio of Na2S2O8 to EDOT was 1.3:1, reaction temperature was 20℃, solid content was 2.4%, and the solution did not need to add any more acid to change the p H value. Under the condictions, the surface resistancy of PEDOT/LS was 49.2 kΩ/sq, the particle size was approximately 447 nm. And the particles could disperse stably in water in shape of ball.Acidic and neutral antistatic coatings have been prepared using PEDOT/LS as conductive compotent and applied to glass sheet. The film is smooth, the surface resistance was less than 108 Ω/sq. It has good water-resistance, thermal stability and it meet the standards of antistatic films.Tests showed that the structure of PEDOT/LS particles is: the stoichiometric PEDOT/LS polyelectrolyte complex stays in the inner core and excess of hydtophilic LS cover on the surface, forming a shell around the gel particle. LS acts as the dopant as well as disperant of PEDOT. The interactions between them include π-π interaction and electrostatic acctraction.Oxidative PEDOT dedoped when alkali was added into the PEDOT/LS suspension, and then the colour of PEDOT/LS changed from blue to purple. Also, the surface resistancy of PEDOT/LS films increased. If we add acid into them, the reductive PEDOT redoped and became conductive again. But the level of redope differ with various alkalility.