Synthesis And Performance Of Thiophene-based Self-cross-linkable Graphene Dispersants

The excellent properties of graphene have attracted great interest.However,theπ-πinteractions between graphene sheets make it difficult to disperse,which greatly limits the applications of graphene.There are mainly covalent and non-covalent modifications to disperse graphene,and covalent modifications can destroy the structure of graphene,while non-covalent modifications are of more interest because they can maintain the excellent properties of graphene.However,the problem of poor dispersion and high dosage of traditional surfactants on graphene cannot be ignored,and the excessive presence of dispersant on the surface of graphene will affect the performance of graphene.Therefore,it is important to prepare dispersants with high dispersing ability,additional functionality,or can be removed from the final composite system.In this paper,two thiophene-based graphene dispersants were prepared using the thiophene ring as the conjugate group and providing hydrophilicity through the silicone hydroxyl group,and the properties of the dispersants were investigated,and the results showed that the dispersants possessed good graphene dispersion properties.Using the self-crosslinking property of silica hydroxyl groups,the carbon matrix films were prepared,and the tensile property test proved that the self-crosslinking ability of the dispersants could enhance the mechanical properties of the composites.Experiments related to dispersant removal were conducted on the carbon matrix film,and the related tests showed that the dispersant could be successfully removed in the carbon matrix film after the treatment.The main research contents and results of the paper are as follows:1.A highly reactive dispersant DSi TP with the thiophene ring as the conjugate center and rich in silicon hydroxyl groups was synthesized.The DSi TP precursor was prepared by a one-step reaction using thiophene-2-methylamine as the graphene-friendly end material and 3-glycidoxypropyltrimethoxysilane（GPTMS）with rich silicon methoxy（Si-O-CH₃）as the hydrophilic end material,DSi TP rich in silicon hydroxyl groups（Si-OH）was obtained using formic acid hydrolysis.The thiophene ring was adsorbed on the graphene surface byπ-πconjugation,the silicon hydroxyl group was a hydrophilic group,and the positive charge of quaternary ammonium N provided mutual repulsion,which successfully dispersed graphene stably in water.The minimum mass ratio of dispersant to graphene was 1:3,and the maximum dispersion concentration of graphene was 3 mg/m L.Self-crosslinked carbon-based membranes were prepared by abstraction through the good reactivity of the terminal silica hydroxyl groups of the dispersant.After a simple oxidation treatment to disrupt the interaction between DSi TP and graphene,the dispersant could be removed from the film to improve its electrical conductivity.The experimental results showed that the removal of DSi TP from the carbon-based film could reach 27.5%and the film resistance value decreased by 12.5%.2.Based on the previous work,C=N bond was constructed on the thiophene ring as a way to expand the conjugated area and further enhance the dispersant’s ability to disperse graphene.The dispersant precursor was produced using thiophene-2-carbaldehyde,ethylenediamine and GPTMS as raw materials.The precursor was hydrolyzed to obtain the dispersant DSi TE with enhanced dispersing ability.Compared with the previous dispersant DSi TP,the minimum mass ratio of dispersant to graphene could be reduced to 1:4 due to a larger conjugated area,and the maximum dispersion concentration of graphene was enhanced to 4 mg/m L,and DSi TE also retained good self-crosslinking film-forming properties.The C=N bond structure can be hydrolyzed under acidic conditions,and the dispersant can be removed from the film by simple acid treatment to destroy its structure.It was found that the removal rate of DSi TE from the self-cross-linked carbon based film could reach 29.5%and the film resistance could be reduced by 24%.