Synthesis and Physical Vapor Deposition of Low-Molecular-Weight Poly(3,4-ethylenedioxythiophene)

Abstract

Thin films of poly(3,4-ethylenedioxythiophene) (PEDOT) were obtained by physical vapor deposition. To this end, low-molecular-weight PEDOT was synthesized by oxidative polymerization using oxygen as the oxidizing reagent with palladium acetate and copper acetate as the catalysts. The degree of polymerization was controlled by adjusting reaction time. The material can be vapor-deposited by thermal evaporation when the degree of polymerization was about 10. Formation of PEDOT thin films was confirmed by infrared spectroscopy. The optical absorption edge of the deposited film showed a redshift with increasing degree of polymerization. The electrical conductivity of the deposited film was in the range from 10-4 to 10-3 S/cm. The deposited films are expected to be in the nondoped state since the oxidizing reagent (oxygen) is unlikely to remain in the films.