Studies On Preparation And Properties Of Flexible Polyaniline Based Conductive Hydrogels

With the rapid development of portable and wearable electronic devices,energy storage equipment with flexible property has become a new research field.Flexible supercapacitors can have a variety of shapes in a specific state,and their comprehensive performance is directly affected by the performance of electrode materials.Therefore,electrodes with high performance and flexible properties become an important factor to prepare the flexible supercapacitors.In this paper,polyaniline?PANI?hydrogel was prepared by using phytic acid as doping agent and gel factor,since phytic acid can react with more than one PANI chains.Then,highly flexible and conductivity PANI based hydrogels were prepared by adding different flexible supporting materials and other conductive materials.Structure and properties of the obtained PANI based hydrogels were investigated in detail.?.Preparation of Ag NPs-PANI composite hydrogels and their propertiesIn order to improve the conductivity of PANI hydrogels,silver nanoparticles?Ag NPs?were used to combine with PANI.Firstly,aniline,phytic acid,silver nitrate?AgNO₃?were mixed.Aniline was oxidized and form hydrogel by doping and crosslinking with phytic acid.At the same time,silver nanoparticles?Ag NPs?were reduced in situ by aniline.The reduced Ag NPs were uniformly attached to PANI fibers for formation of Ag NPs-PANI hydrogel.Then,the Ag NPs-PANI flexible electrode was obtained by directly coated the Ag NPs-PANI hydrogel on hydrophilic carbon cloth,which was used as flexible supporting material.Due to the uniform distribution of Ag NPs in PANI hydrogels,the conductivity of the Ag NPs-PANI hydrogel flexible electrode was increased to more than one order of magnitude compared with pure PANI hydrogels.At the current density of 0.5 A·g^-1,the specific capacitance was about379 F·g^-1.?.Preparation of GN-PANI composite hydrogels and their propertiesGraphene hydrogels have been proved to have good conductivity and flexibility.Thus,highly flexible and conductive hydrogels could be obtained by combination of PANI with graphene hydrogels.Firstly,graphene oxide dispersed in deionized water with concentrations of 2 mg·mL^-1,3 mg·mL^-1 and 4 mg·mL^-1,respectively.Graphene oxide hydrogel was then prepared by hydrothermal method and reduced to GN hydrogel by hydrazine hydrate.In the case of the concentration of 2 mg·m L^-1,the GN hydrogel showed well three-dimensional porous microstructure.The PANI-GN composite hydrogels were further prepared by in-situ polymerization of aniline in the prescence of phytic acid with a certain proportion of GN hydrogel.When the mass ratio of graphene to PANI was 1:100,the PANI-GN composite hydrpgel had higher specific capacitance.At the current density of 0.5 A·g^-1,its specific capacitance was 286 F·g^-1.The specific capacitance of the composite hydrogel could be kept to 88%after 1000 times of charge and discharge circles at current density of 1 A·g^-1.?.Preparation of PANI-PVA composite hydrogels with interpenetrating networks and their properties?.Preparation of PANI-PVA composite hydrogels and their propertiesIn order to further improve the flexibility of the PANI hydrogels,polyvinyl alcohol?PVA?was used as flexible support material.The PANI hydrogels were formed directly in PVA aqueous solution.Then PANI-PVA composite hydrogels formed a continuous interpenetrating network structures through several freeze-thaw cycles,which process induced the closely cross-linked together among the PVA and PANI chains.This structure gave the hydrogels with good flexibility and strength.Moreover,it provided a channel for the efficient transport of electrolyte ions.The structure of composite hydrogels was affected by the cycle numbers of freezing and thawing.Compared with the hydrogel without freeze-thaw cycle,the PANI-PVA composite hydrogels showed more continuous structure and high specific surface area,resulting in the increase of the compression strength and capacitance of the composite hydrogel.However,after four time of freeze-thaw cycles,the gel structure and capacitance was no longer changing with the increase of freeze-thaw times.The specific capacitance of the PANI-PVA interpenetrating hydrogel was 314 F·g^-1 at the current density of 0.5 A·g^-1.Moreover,the PANI-PVA interpenetrating network hydrogel showed excellent flexibility.After folding 180°for 100 folds,the properties of the hydrogel could be maintained to 96%of the original value.Therefore,the flexible PANI-PVA hydrogels had latent applied value on flexible electrode of supercapacitors.