Preparation And Application Of High Resilience And Self-healing Conductive Hydrogel

Because of their excellent biocompatibility,flexibility and water absorption,hydrogels are widely used in biomedicine,electronics and other fields.However,although hydrogels crosslinked by chemical bonds have good mechanical properties,it has no self-healing propertiesit.Although physically crosslinked hydrogels have better self-healing properties,they usually have low stability and poor mechanical properties.Compositing electroactive substances（such as carbon materials,nanoparticles,conductive polymers）can produce electrically conductive hydrogels with electrical response.However,the doping of electroactive substances will lead to the embrittlement of hydrogel,and the insulating hydrogel backbone will also reduce conductivity.Therefore,the development of hydrogels with high mechanical properties,self-healing and conductivity is of great significance.Based on this,a series of high resilience,self-healing and conductive hydrogels were designed and synthesized,and their applications in flexible supercapacitors were explored.The main research contents and conclusions are as follows:（1）Based on the mechanism of micelle polymerization and hydrophobic interaction,a double-crosslinked hydrogel（PCDC）was prepared by using lauryl sodium sulfate-octadecyl methacrylate（SDS-C18）micelle as physical crosslinkers,and amphiphilic polyether modified polysiloxane（Si PU）nanoparticles terminated by methacrylic acid as chemical crosslinkers and acrylamide（AM）as monomer.The tensile strength of the prepared PCDC hydrogel was higher than 130 k Pa,the elongation at break was over 710%,and the original state of the prepared hydrogel could be restored rapidly in cyclic tensile and cyclic compression tests,showing excellent stretchability,strength and resilience.In addition,hydrogels also exhibited significant self-healing behavior,which could be re-bonded between the cutting surfaces without external stimulation,and could achieve 71%self-healing effect in 20 minutes.（2）Using the"one pot"method,carbon nanotubes（CNTs）and the above gel matrix were mixed to prepare conductive hydrogel（DCPU）.The effects of crosslinkers content,water content and CNTs content on the properties of hydrogels were studied.When the Si PU content was 0.3 g,the water content was 82%and the CNTs content was 0.1 g,the prepared hydrogel（DCPU-4）had the best comprehensive performance.DCPU-4 could achieve 415%elongation at break and 225 k Pa tensile strength.Under the condition of 50% compression deformation,cyclic compression could achieve rapid shape recovery and good resilience.Hydrophobic interactions gave good reparability to hydrogels and achieve 50%self-healing effect without external stimulation.The conductivity of the conductive hydrogel was 0.0270S/m,and the conductivity decreased with the increase of elongation.It had excellent tensile deformation-electrical response and stable conductivity,and could maintain 78.9%of the initial conductivity at 50%elongation.The double layer capacitor assembled by DCPU hydrogel electrode had good capacitance stability.However,there stil had some problems such as smaller specific capacitance.（3）In order to increase the capacitance,two kinds of pseudo capacitance materials of polypyrrole（PPy）and cobalt tetroxide Co₃O₄ were introduced into the CNTs conductive hydrogel system respectively.Two kinds of PPy/CNTs and Co₃O₄/CNTs composite hydrogel electrodes were successfully prepared.Inspired by mussel-like structure,PPy and Co₃O₄ were hydrophilically modified by dopamine（PDA）.SEM results showed that modification of PDA not only made PPy and Co₃O₄ disperse evenly,but also increased the crosslinking density and viscosity of the network.PPy/CNTs and Co₃O₄/CNTs conductive hydrogels had excellent stretchability,tensile strength,resilience and self-healing properties（self-healing effect is 33%and 74%respectively）.The conductivity（0.0056 S/m and 0.0023 S/m）could be maintained at10%elongation,distortion and 1000 cyclic fold in half.The supercapacitor fabricated by composite hydrogel electrode had a better specific capacitance（PPy/CNTs is 65.5 m F/cm²and Co₃O₄/CNTs is 5.8 m F/cm²）.Through the 50 cyclic CV curve test and 30 degree bending test,it was found that all CV curves coincided completely,indicating that the capacitor had good capacitance stability.