Preparation And Electrical Properties Of PEDOTs-based Intrinsic Selfhealing Composites

Conducting polymer films and devices are vulnerable to mechanical,chemical,aged,illumination radiation and other effects in their application,resulting in crack and damage,which seriously damage their structural,electrical and mechanical properties.The self-healing ability of conducting polymer can greatly enhance the reliability and prolong the service life of the device.Poly（3,4-ethylenedioxythiophene）:poly（styrene sulfonate）（PEDOT:PSS）is a kind of famous aqueous dispersible conducting polymer with excellent processability,high transparency in the visible light range and flexibility,which is widely used in solar cells,light emitting diodes,transparent electrodes,supercapacitors and biosensors.Considering that the colloidal particles of PEDOT:PSS are easy to aggregate,and the initial film has the problems of low electrical conductivity,easy moisture absorption,and easy damage to form scratches,this paper studies the influencing factors of self-healing properties of PEDOT:PSS film from four aspects:processing methods,conductive accelerator treatment,main chain structure control and inorganic additives regulation.The specific research contents and results are as follows:1.Effect of processing methods on self-healing properties of PEDOT:PSS films.The storage temperature of PEDOT:PSS dispersion is generally required to be 5-10℃,and the shelf life is only 9 months.The preparation of the dispersion into stable materials is conducive to transportation and storage.In this paper,PEDOT:PSS dispersion was treated by freeze-drying and oven-drying methods and then redispersion.Compared with the method of oven-drying,the freeze-drying is more feasible.The results showed that the redispersed PEDOT:PSS perfectly retained the initial characteristics,such as p H（about 1.64 at 25℃）and viscosity（about 81.7 m Pa·s at25℃）,and the solid content remained below 1.4 wt.%.There was no significant difference in the electrical properties and surface morphology of the film,and healing rate was up to 97%.2.Effect of conductive accelerator on self-healing properties of PEDOT:PSS films.In most applications of PEDOT:PSS,the conductivity of the film will be improved by adding conductive promoting solvent.The effects of conductive solvents such as ethylene glycol（EG）,polyethylene glycol（PEG）,dimethyl sulfoxide（DMSO）,isopropyl alcohol（IPA）and concentrated sulfuric acid（H₂SO₄）on the self-healing properties of PEDOT:PSS films were studied and the corresponding mechanism was clarified.The results showed that the crack width of the EG treated film was significantly reduced and the conductivity was restored by 78%.After PEG treatment,the cracks were obvious and the electrical conductivity could be increased to 10 S cm^-1and the healing rate was 94%.DMSO treatment did not achieve healing.After H₂SO₄post-treatment,the crack width decreased,and the conductivity promoted 23 times but the healing rate was only 47%.3.Effect of conductive accelerator on self-healing properties of poly（3,4-ethylenedioxyselenophene）:poly（styrene sulfonate）（PEDOS:PSS）films.In order to further verify whether the effect of conductive promoting solvents on self-healing properties is widespread in the PEDOT:PSS analogues,the selenium analogue PEDOS:PSS was taken as the representative to study the effect of EG,PEG treatment and concentrated H₂SO₄ post-treatment on the electrical and self-healing properties of the films,and the corresponding mechanism was clarified.The results showed that,similar to PEDOT:PSS,EG treatment improved the healing rate by 58%.The cracks were obvious after PEG treatment,and the conductivity could recover 68%.After H₂SO₄ post-treatment,the conductivity was increased by 80 times but the healing rate was only 29%.Since the application of PEDOTs:PSS film is closely related to various additives or post-treatment,this study helps to clarify the relationship between photoelectricity and self-healing behavior of conducting polymer films.4.The effect of inorganic cage polyhedral oligomeric silsesquioxanes（POSS）on the self-healing properties of PEDOT:PSS films.Due to the great influence of water-enduced healing process on the surface of the film,POSS which can improve the toughness and hydrophobicity of the film was added into PEDOT:PSS in this paper.A series of compact and uniform composite conducting polymer films were prepared by drop coating and spin coating methods.The effects of POSS on the surface morphology,hydrophobicity and electrical properties of PEDOT:PSS film were studied.Under the optimized ratio,the introduction of POSS can not only improve the electrical properties of PEDOT:PSS film,but also promote its hydrophobicity.The composite film showed excellent stability under long-term immersion in water,but weakens the water-enduced healing performance of the film.