Preparation And Sensing Properties Of Polyaniline/Lithium Bromide/Polyvinyl Alcohol Flexible Conductive Hydrogels

Conductive hydrogels have great application potential in flexible sensors.When materials respond to external stimuli,the structural changes of the conductive network inside the materials will affect the resistance value of the hydrogels.Through the introduction of conductive materials into the flexible hydrogel system,the modification of hydrogel materials can be realized.Through the grafting and polymerization of conductive materials in the system,the internal three-dimensional structure and conductive network of materials can be formed to improve the mechanical properties and conductive ability of materials.Therefore,based on the defects of electrical conductivity and tensile strain properties of PVA hydrogel,canalions and conductive polymer polyaniline were introduced.The composite hydrogels with excellent conductivity,high strain sensitivity and suitable for motion monitoring were prepared by the influence of the characteristics of canalions and conductive polymers.In this study,polyvinyl alcohol was used as the base,polyaniline as the conductive material,and lithium bromide(Li Br)was used to modify and doping the material.PANI conductive hydrogel with excellent performance was prepared by chemical oxidation of polyaniline and 1 mol/L hydrochloric acid(HCl)as proton acid doping.The conductive hydrogel has excellent strain capacity and high conductivity,which can quickly respond to external stimulus changes and good frequency response effect.It is an ideal material for flexible hydrogel sensors.The specific research contents are as follows:(1)Using polyvinyl alcohol as the base material and introducing different mass fractions of lithium bromide to prepare ionic hydrogels by freeze-thaw method.Using the Hofmeister effect of Yin and Yang ions on large molecular chains of polyvinyl alcohol,the internal three-dimensional pore structure of the hydrogels was adjusted to prepare hydrogels with structural differences.The internal functional group structure of the material was tested by infrared spectrum,the microscopic morphology of the material was tested by scanning electron microscopy,and the crystallinity of the material was tested by X-ray diffraction.The physical effect of salt ions on the material was reflected through the changes of electrical conductivity and tensile strength,and the sensing effect of the material was analyzed.Physical modification of ionic hydrogels by salt ions in the preparation of ionic hydrogels.During the process,salt ions improve the conductivity and tensile strength of the hydrogel without damaging the three-dimensional internal structure of the material.Compared with the pure 10 wt% polyvinyl alcohol hydrogel,when the mass fraction was 15%,the conductivity of ion-conductive hydrogel increased by about50%,reaching 135.10 m S/m,and the maximum stress of ion-conductive hydrogel reached 245.00 k Pa,2.5 times of the tensile stress of pure PVA hydrogel.The corresponding tensile strain reached 247%,which was 53% higher than that of pure PVA hydrogel.The feasibility of applying the ionic conducting hydrogel to sensor field was determined.(2)Based on the original ionic hydrogel,polyaniline conductive material was introduced to improve the conductivity and mechanical properties of the material.Polyvinyl alcohol was dissolved in acidic solution,and then aniline monomer(AN)was introduced into the material under the condition of ice water bath.Ammonium persulfate(APS)was used as initiator and hydrochloric acid as dopant.Polyaniline material was in-situ polymerized in colloidal solution,and a double cross-linked network was formed through hydrogen bonding between polyvinyl alcohol and polyaniline.While maintaining the three-dimensional structure of the material,the conductivity and mechanical properties of the material are improved,and the toughness of the polyaniline material is obviously improved after the introduction of the material.By infrared analysis,scanning electron microscopy and X-ray diffraction analysis,the structural changes and chemical composition of the materials after in-situ polymerization were analyzed.At the same time,the effects of different contents of aniline on the electrical and mechanical properties of the materials after in-situ polymerization of hydrogel were explored.It was found that when aniline concentration was 20.00 mg/m L,the composite hydrogel could maintain excellent strain and mechanical properties.The conductivity of the hydrogel can reach 2257.72 m S/m,the mechanical tensile property can reach326.70 k Pa and the tensile strain can reach 454%.It shows that the introduction of polyaniline material can effectively improve the performance of the material,so that the material is more suitable for the sensor,which is a kind of excellent performance of hydrogel sensor.