Preparation And Properties Of The Flexible PEDOT/PSS-HNTs Film

Since the discovery of conductive polymer polyacetylene in 1978, other conductive polymers such as polyaniline, polypyrole, polythiophene and its derivatives as well as polyparaphenylenevinylene were synthesized. Among them, conductive polymer poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate)(PEDOT/PSS) is a colloidal dispersion, with good thermal and chemical stability, high conductivity and high transmittance in visible light region. Therefore, it has become the focus of researches. On the other hand, Halloysite nanotubes(HNTs) are natural nanoclay materials with a rich resource, it has larger specific surface area, high length diameter ratio, good mechanical properties. These advantages make HNTs have a wide range of applications in many fields.Previously we found that completely insulating HNTs significantly enhance electrical conductivity of PEDOT/PSS films by simply mixing, and we obtained conductive and highly porous PEDOT/PSS-HNTs hybrid films. However, these films had no good flexibility and mechanical properties. It is expected that water-soluble polymers can improve the PEDOT/PSS film and PEDOT/PSS-HNTs hybrid films.In this thesis, firstly we used PEG as the water-soluble polymer to improve the mechanical properties. We prepared PEDOT/PSS films after adding PEG into PEDOT/PSS dispersion. As a result, mechanical properties of PEDOT/PSS film were enhanced, i.e., when the solid content of PEG is 41.1 % in the film, it’s breaking strain is 19.8 %, the Young’s modulus is 0.32 GPa and the conductivity is 216.7 S/cm. Based on this result, we additionally added HNTs into the dispersion to prepared the hybrid films. However, the electrical conductivity of the films is declined compared with the films without HNTs. We optimized the content of HNTs and PEG in the mixed solution to obtain better conductivity and mechanical properties. As a result, we found that, when the content of HNTs is 3 wt.% in the system, the conductivity and folding resistance of the composites were better than the film with content of HNTs is 4 wt.%, while their mechanical properties were similar.Secondly, we used two kinds of PVA having different molecular weight to prepare aqueous solution of 9 wt.%. When using low molecular weight PVA and the weight ratio of PEDOT/PSS to PVA in composites is 1:9, it’s breaking strain reached 190 %. When using high molecular weight PVA, the electrical conductivity of composites is 5 S/cm, moreover, the flexibility of the film is good. We additionally added HNTs into dispersion to prepare the hybrid films while the amount of HNTs in the mixed solution was 4 wt.% and the molecular weight of PVA is 16000. When the weight ratio of PEDOT/PSS to PVA was 9:1, the conductivity of the film is 59.4 S/cm, while the film was brittle. On the other hand, when we used PVA with molecular weight of 146000-186000, PEDOT/PSS-HNTs-PVA hybrid film(weight ratio of PEDOT/PSS to PVA is 1:9) showed low conductivity, breaking strain(14.5 %) and Young’s modulus(0.3 GPa).