Research On The Properties Regulation And Electromagnetic Shielding Application Of PEDOT:PSS-based Conductive Composite Hydrogels

Conductive hydrogels are mainly composed of polymer networks,conductive fillers and water and other raw materials,with porous structure and stretchability,and have broad application prospects in the fields of energy storage,sensing and electromagnetic shielding.As a common conductive polymer,poly（3,4-ethylenedioxythiophene）:poly（styrene sulfonate）（PEDOT:PSS）has become an important candidate for conductive fillers due to its high chemical stability and good water solubility.However,the dispersive long-chain PSS limits the conductivity of PEDOT.Solvents such as sulfuric acid（H₂SO₄）and dimethyl sulfoxide can destroy the electrostatic interaction between PEDOT and PSS,increase the crystallinity of PEDOT itself and improve its conductivity,but it will inevitably cause the mechanical strength of hydrogels to decrease,resulting in limited application in the field of flexible electromagnetic shielding.MXene nanosheet is a new electromagnetic shielding material with high conductivity and rich surface functional groups,which can not only improve the conductivity,but also is expected to form hydrogen bonds with polymer networks to improve the mechanical strength of hydrogels.In this paper,PEDOT:PSS conductive hydrogels were prepared using polyvinyl alcohol（PVA）with low cost,good biocompatibility and high viscosity as the polymer network and PEDOT:PSS as the conductive filler,and the regulation of H₂SO₄ and MXene on its mechanical and electrical properties was studied.On this basis,the electromagnetic shielding characteristics and physical mechanism of MXene/H₂SO₄/PEDOT:PSS/PVA hydrogels were studied.The specific research content is as follows:（1）Study on the regulation of mechanical and electrical properties of PEDOT:PSS-based conductive composite hydrogels.Firstly,the effects of H₂SO₄ concentration（0-18 mg/m L）and MXene concentration（0-25 mg/m L）on the elastic modulus and conductivity of PEDOT:PSS/PVA hydrogels were studied.The results showed that the elastic modulus of PEDOT:PSS/PVA hydrogels decreased（increased）with the increase of H₂SO₄（MXene）concentration,and the conductivity increased（increased）with the increase of H₂SO₄（MXene）concentration.We used Infrared spectroscopy,Raman spectroscopy,and X-ray photoelectron spectroscopy to analyze the reason that H₂SO₄ reduces the formation of borate ester bonds and promotes the conversion of PEDOT:PSS to linear conformation,which improves electron transport but reduces mechanical strength.MXene increased the hydrogen bond crosslinking sites and the charge transport between it and PEDOT:PSS,which improved its mechanical strength and promoted charge delocalization.Secondly,the concentration ratio of H₂SO₄ and MXene was optimized,and the ultimate tensile strength of PEDOT:PSS/PVA hydrogel was increased from 38 k Pa to 180 k Pa,and the conductivity was increased from 0.027 S/m to 0.095S/m.（2）Study on electromagnetic shielding characteristics and mechanism of PEDOT:PSS-based conductive composite hydrogels.Firstly,the electromagnetic parameters of MXene/H₂SO₄/PEDOT:PSS/PVA hydrogels were tested in the X-band（8-12.4 GHz）by waveguide method and the electromagnetic shielding mechanism was analyzed.After H₂SO₄and MXene treatment,the electromagnetic shielding efficiency of PEDOT:PSS/PVA hydrogel increased from 30 d B to 40 d B,which was mainly attributed to the increase of impedance mismatch after the increase of conductivity,the increase of macroscopic current caused by carriers,and the enhancement of reflection and conduction loss.On the other hand,the increase in the number of interfaces and the polar surface functional groups of MXene increase the polarization loss.Secondly,the electromagnetic shielding characteristics of MXene/H₂SO₄/PEDOT:PSS/PVA hydrogels in the P band（12.4-18 GHz）and K band（18-26.5GHz）were studied.It was found that the shielding efficacy of hydrogels increased linearly with the increase of electromagnetic frequency,because with the increase of frequency,the impedance matching degree and attenuation constant increased,and the absorption loss increased linearly.The average shielding efficiency of MXene/H₂SO₄/PEDOT:PSS/PVA hydrogels was 40 d B in the X-band,57 d B in the P-band,84 d B in the K-band,and maintained a shielding effect of 94.5%under 200%deformation,and the shielding efficiency recovered by about 98%after 1 min of self-healing damage.