.3,4 - Ethylenedioxythiophene Dioxythiophene Synthesis

Poly(3,4-ethylenedioxythiophene)(PEDT) is one of the important conducting polymers,which can be doped with poly(styrene sulfonic acid )(PSS) to prepare PEDT/PSS multiple films.This kind of films possesses high conductance(10s/cm) and visible light transmission,strong mechanical intensity and excellent stability,farther more,which is easy to be manufactured.Recently,the polymer has been able to develop successfully the application of solid electrolyte capacitors and antistatic coatings on plastic.In addition,it can also be applied in far-ranging fields,such as through-hole plating of printed circuit board,photodiodes,solar batteries,sensors,electromagnetism materials,etc.However,the synthesis of 3,4-ethylenedioxy- thiophene(EDOT),as the monomer of PEDT,is very difficult,which causes the high price of EDOT.Nowadays, all the EDOT used in China are imported,which limits the application of PEDT.Hence, it is significant to reduce the cost and improve the synthetic procedures of EDOT.In this paper,we focus on the synthesis methods and techniques of EDOT.The synthesis of EDOT is adopted a five-step synthesis method of Jonas,which includes esterification, cyclization,aether exchanging,hydrolyzation and decarboxylation.The last step, decarboxylation,is the key step for the yield of EDOT.The other four steps are easy in their synthesis reactions and should produce the high yields with above 80%,which is agreement with the mass-producing.However,the decarboxylation reaction is very difficult due to the reaction conditions are so hard,and up to now,the highest yield of this reaction is only 60%.Based on a large amount of experiments,several kinds of catalysts and solvents are changed in this paper.Using 2,5-dicarboxylic-3, 4-ethylenedioxythiophene as the raw material,the synthesis technology is improved by using orthogonal experimental design to get the optimal technologic parameters. Under the optimal technologic parameters,the yield of EDOT is increased to 85%, which is improved 25%compared with reporting;the purity of EDOT is above 99%;the reactive temperature is 160℃,which is reduced 20℃compared with the references. Especially,the reactive time is only 2 hours,which is shortened 10 hours.In addition, the environment pollution and poison side-effect are reduced by using polyatomic alcohol instead of quinoline.At last,the mechanisms of dicarboxylation of 2,5-dicarboxylic-3,4-ethylene dioxythiophene, catalysis and solvent effect are discussed in details...