Preparation And Properties Of Dynamically Covalent Polymer/Graphene Aerogel Conductive Composites

Graphene has received wide attention since its discovery,and the emergence of graphene aerogels was significance.Graphene aerogels have many excellent properties and show great potential in the fields of catalysis,electronic devices and detectors.In addition,the composite of organic polymer and graphene aerogels is also an important research branch.The obtained materials often possess both excellent properties of aerogels and flexibility,processability and excellent mechanical properties provided by organic polymer substrates.However,most of these materials can not be repaired and recycled,and are not environmentally friendly.Dynamic covalent chemistry(DC_VC)is a new concept in organic chemistry,the main merit of which in the field of polymer is to provide ductility and repairability enabled by the reversibility of chemical bonds.As one of the most important dynamic covalent chemistry,imine(-C=N-)chemistry has been widely used in covalent organic frameworks,organic molecular cages,and polyimide materials.In this thesis,polyimines are employed as the substrate for the graphene aerogel based compositions,which combine the dynamic covalent chemical properties and excellent properties of graphene aerogels.Furthermore,the hybride polyimide polymer substrates were prepared via imine chemistry for polyimide/graphene aerogel composites,which are repairable and have high conductivity.The specific work is as follows:(1)Preparation and properties of graphene aerogel/Polyimine conductive composite filmsThe graphene aerogel is made into powder and then mixed with the monomer of the polymer in the solution.After the evaporation of the solvent by heating,the system can be solidified into PI-a GAs.The original three-dimensional porous microstructure of graphene aerogels could be maitained in the resulting composites,leading to a high conductivity up to 161 S/m.In addition,different from the traditional thermosetting matrix,polyimine not only has good mechanical properties and chemical stability,but also has the ability of bending,stretching,rehealing and closed-loop recycling,which can greatly reduce the negative impact of the resulting electronic waste on the environment.Therefore,polyimine graphene aerogel based composite PI-a GAs can be used as an excellent candidate for flexible electronic devices.(2)Preparation and properties of three-dimensional graphene aerogels/polyimine conductive CompositesThe remolded columnar 3-dimensional graphene aerogel/Polyimine composite(m PI-a GAs)was prepared by infiltrating the polyimine monomer in the solution into the three-dimensional pore structure of the graphene aerogel followed by curing.The prepared m PI-a GAs has excellent and durable compressibility,high compressive strength up to 120 MPa and high conductivity up to 100 S/m.In addition,by adjusting its components,these characteristics can be adjusted to meet the needs of various applications.Combined with the above properties,m PI-a GAs can be used as an excellent compression variable resistance material in the field of flexible electronic devices with high requirements for size,durability and accuracy.In addition,under the conditions of simple repair and healing,the composite can be restored without any special curing agent,and the electrical conductivity and compressive strength can be maintained.This is rarely reported in the field of flexible electronic materials,which is of great significance to reduce the overall production cost of materials and reduce the generation of electronic waste.(3)Preparation and properties of graphene aerogels/polyimide conductive composite membranesIn this part,three kinds of aromatic dianhydride monomers and three kinds of common aromatic diamine monomers with different conjugation structures were selected to design and synthesize nine kinds of amino terminated imide monomers which are suitable for imine polycondensation.Among them,three kinds of imides with high yield were selected.The mechanical properties and recyclability of the hybrid films were studied:the tensile strength of the hybrid films can reach 93 MPa,and the tensile modulus can reach 3.2 GPa.The mechanical properties of all film materials can be restored to more than 95%of the original.The conductivity of 5 wt%graphene aerogel loaded film material can reach up to 50 S/m,which could be further adjusted by changing the monomer structure.This finding also provides a new idea for future research.