Study And Application Of Flexible Conductive Materials Based On Ionogel

Ionic liquids have many excellent physical and chemical properties,such as very low vapor pressure,ability to remain liquid state in a wide temperature range,good thermal stability,and easy controllable dissolution capacity.Ionogel can immobilize IL in the gel phase,conducting charged ions or modifying other conductive materials that work as flexible conductive materials.We have prepared graphene film materials using a scalable and flexible climbing strategy,and illustrated its synthesis and electrical conductivity;based on the climbing strategy,a graphene/ionogel@PEDOT:PSS high-performance hybrid flexible transparent electrode（FTE）was fabricated;the graphene/ionogel@PEDOT:PSS was applied as both FTE and electrochromic layer in electrochromic devices;A triblock-polymer-based physical-chemical crosslinked conductive ionogel with high mechanical strength was prepared.The main content works of this paper are as follows:1.We started from liquid exfoliated few-layer graphene dispersion,utilizing the self-climbing effect driven by surface tension to fabricate graphene film at the air-water interface and transferred to a flexible substrate via wetting-induced climbing strategy.The size distribution of graphene sheets is restricted by designing centrifugal conditions,and the optimal conditions for preparing graphene films are obtained.The general rule for size distribution of graphene was obtained through Raman spectroscopy and scanning electron microscopy.It was proved that graphene sheets obtained via liquid exfoliation by ball milling have better conductivity than graphene oxide and reduced graphene oxide.The thickness of the graphene layer was characterized by ellipsometry.The causes of affecting the thickness of the graphene film were explained,and the mechanism of conductivity in graphene film was demonstrated.2.We combined the climbing strategy of graphene film and hybridization with ionogel and PEDOT:PSS,a high-performance graphene/ionogel@PEDOT:PSS ternary hybrid FTE was fabricated.With the combination of wetting-induced production of graphene film and ionogel-mediatedπ-πinteraction between PEDOT chains and graphene,the graphene/ionogel@PEDOT:PSS trinary hybrid FTE exhibits excellent mechanical flexibility,good optical transparency of 88%and low sheet resistance of 30Ωsq^-1,greatly enhancing electrical conductivity of liquid-exfoliated graphene.The distribution of graphene/ionogel@PEDOT:PSS at the molecular level was obtained,the corresponding structure and mechanism of enhancement in conductivity was further clarified.3.A flexible electrochromic device based on graphene/ionogel@PEDOT:PSS trinary hybrid FTE was prepared,in which graphene/ionogel@PEDOT:PSS serves as both transparent electrode and electrochromic layer.Compared with other ITO-free flexible electrochromic device with a similar three-layer structure reported by previous workers,our device exhibits higher electrochromic contrast and faster switch of response under lower working voltage,as well as better electrochemical and mechanical stability,benefiting from the excellent photoelectric properties of graphene/ionogel@PEDOT:PSS trinary hybrid FTE.4.A high-performance conductive ionogel with excellent mechanical strength,flexible processability and high adhesion was prepared through self-assembly of an ABA triblock copolymer poly（styrene-b-ethylene oxide-b-styrene）（PS-PEO-PS）and in situ crosslinking polymerization of an IL,1-（4-vinylbenzyl）-3-butylimidazolium bis-（trifluoromethylsulfonyl）imide（[VBBIm]NTf₂）.The introduction of both physical and chemical crosslinking into the self-assembled ionogel can improve the mechanical properties largely.The mechanism of improving mechanical properties of the physical-chemical crosslinked ionogel was illustrated.It was observed that the two crosslinked networks in the physical-chemical crosslinked ionogel showed a structure of microphase separation and interpenetration.The resulting ionogel could be spray-coated onto a variety of materials from a spray bottle to form a tough and conductive gel membrane because of good adhesion between ionogel and substrates.5.We designed a composite ionogel,i.e.,PEDOT:PSS@P[VEIm]DCA,by electrostatic interaction and ion exchange between PEDOT:PSS and ionogel.The resulting semi-interpenetrating structure endows the composite ionogel with free-standing properties,high stretchability and conductivity.We also developed a strategy of fabricating composite ionogels with reversible in-plane folding-unfolding property.