Preparation And Electrical Conductivity Properties Of Graft Modified Graphene Reinforced Polymeric Hydrogels

Electrically conductive hydrogels have potential applications in the fields of electronic skin,flexible sensor,and so on.The preparation of electrically conductive hydrogels with excellent mechanical properties and electronic properties is the basis for their applications.Graphene exhibits excellent mechanical properties and electronic properties,making it ideal nanofiller for the preparation of electrically conductive composite materials with high strength.Therefore,this thesis focused on the preparation of graphene reinforced polymeric hydrogel materials with excellent mechanical properties and electronic properties.Graft modified graphene reinforced polyacrylamide hydrogels were synthesized by polymerization-in situ reduction two-step method and in situ polymerization method,respectively.The purpose of graft modification of graphene is to improve the compatibility between graphene and hydrogel matrix and the dispersion ability of graphene in water.The main research contents and results are as follows:1.Polyacrylic acid grafted graphene oxide(GO-g-PAA)was first synthesized by ceric salt initiated surface graft polymerization of acrylic acid onto GO.Then,GO-g-PAA was incorporated into chemically crosslinked polyacrylamide(PAM)networks to obtain GO-gPAA/PAM composite hydrogel,which were further treated with ascorbic acid solution at ambient temperature to give rGO-g-PAA/PAM composite hydrogels.The structure and morphology of these two kinds of composite hydrogels were studied by FTIR and SEM.It was confirmed that hydrogen bonds exist between the PAA chains on the surface of GO-g-PAA or rGO-g-PAA and PAM matrix.Both GO-g-PAA and rGO-g-PAA have good interface compatibility with PAM matrix,indicating that graft modified graphene is a multi-functional physical cross-linking agent.The equilibrium swelling ratio of GO-g-PAA/PAM(rGO-gPAA/PAM)composite hydrogels decreases with increasing GO-g-PAA(rGO-g-PAA)content.Compared to pure chemical crosslinked PAM hydrogel,the mechanical properties of GO-gPAA/PAM(rGO-g-PAA/PAM)composite hydrogels were significantly improved.The maximum elastic modulus was 2.23 and 2.24 times of pure PAM hydrogel,respectively.The maximum toughness was 2.65 and 3.72 times of pure PAM hydrogel,respectively.Due to the reversible property of hydrogen bonds,GO-g-PAA/PAM(rGO-g-PAA/PAM)composite hydrogels show significant energy dissipation and good self-recovery properties.The maximum recovery rate of GO-g-PAA/PAM and rGO-g-PAA/PAM composite hydrogels reaches 66.9%and 98% after 5 min rest at ambient temperature,respectively.After in situ reduction,the electrical conductivity of rGO-g-PAA/PAM composite hydrogels was significantly enhanced.When rGO-g-PAA content increased to 1.2% of the monomer mass,the electrical conductivity increased gradually to 1.19×10-3 S/m.Moreover,there was significant change in resistance under stretching.2.GO-g-PAA was first reduced by the combination of strong base reduction and glucose reduction to give rGO-g-PAA.Then rGO-g-PAA/PAM composite hydrogels were prepared by in situ polymerization in the presence of rGO-g-PAA.SEM and FTIR analysis showed that rGO-g-PAA was uniformly dispersed in PAM matrix,and that hydrogen bonds exist between the PAA chains on the surface of rGO-g-PAA and PAM matrix.The equilibrium swelling ratio of rGO-g-PAA/PAM composite hydrogels decreased with the increase of rGO-g-PAA content.Compared to pure chemical crosslinked PAM hydrogel,elastic modulus and breaking strength of rGO-g-PAA/PAM composite hydrogels were significantly improved,the maximum of which were 2.8 and 2.3 times of pure PAM hydrogels,respectively.Due to the reversible property of hydrogen bonds,rGO-g-PAA/PAM composite hydrogels exhibit significant energy dissipation and good self-recovery properties.The maximum recovery rate reaches 95% after 5 min rest at ambient temperature.When the content of rGO-g-PAA increased to 0.6% of the monomer mass,the electrical conductivity of rGO-g-PAA/PAM composite hydrogels increased gradually to1.26 10-3 S/m.Furthermore,there was a significant change in resistance upon stretching.