Anisotropic Expansion Of PEDOT/PSS-PAM Hybrid Films

Conducting polymer poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate)(PEDOT/PSS)has been extensively studied from viewpoints of academic and technologic aspects.The PEDOT/PSS has become one of most available conducting polymers since colloidal dispersion of the PEDOT/PSS in water could easily provide films on various substrates by simple means such as solution casting and spin-coating or bar-coating techniques.We found interesting anisotropic expansion of PEDOT/PSS film in water when the PEDOT/PSS was hybridized with water-soluble polymer polyacrylamide(PAM).In this thesis we report the anisotropic expansion in detail.PEDOT/PSS-PAM film was prepared by casting PEDOT/PSS dispersion after mixing with PAM.When the dried hybrid film was immersed in water,we found that in some case,the film area increased to attain to maximum film area which is ca 18 times larger than initial film area.We investigated influences of temperature and p H of water on the expansion of the film area.It was indicated that the maximum expansion of the film area was observed at 35℃ and pH 7,respectively.On the other hand,film thickness decreased during the expansion of the flim area.It is a novel anisotropic expansion of polymer film in water.Furthermore,we investigated the anisotropic expansion on long time scale.It was found that the film area increased in initial stage to attain to maximum film area.Then decreased but not recover to the initial film area.On the other hand,the film thickness slightly increased in initial stage.Then decreased to attain to minimum film thickness,and finally slightly increased but similarly not recover the initial flim thickness.Based on the above experimental results we suggested a plausible mechanism of the anisotropic expansion of the PEDOT/PSS-PAM film.In the expansion water molecules move inside of the film,resulting in size change of the film in water.In initial stage the film thickness rapidly expands since relatively larger amount of water moves inside of the film from area plane.After the water molecules completely move into the inner domain of the film,the film area begins to rapidly increase while the film thickness decreases.After attaining to maximum flim area,the film area decreases and the flim thickness increases since hydrophobic interaction among PEDOT/PSS domains by dissolving of hydrophilic PAM and PSS in water during the expansion.