Study On Preparation And Properties Of Polystyrene/Graphene-based Composite Emulsion

An emulsion stabilized by solid particles instead of organic surfactants is called Pickering emulsion.The 'surfactant-free' character of Pickering emulsion is superior to that of convention emulsion,especially the application in pharmaceutical and cosmetic industry.An increasing number of researcher pay more attention to the outstanding thermal properties of graphene which can be excellent applied to capacitors,sensors and batteries.Because of the poor dispersion,graphene sheet structure is difficult to form graphene-based composite materials.Graphene oxide(GO)which is a derivative of the graphene has been provided a probability to act as stabilizer in Pickering emulsion by introducing the oxygen-containing groups to better improve its hydrophilicity.In our work,the modified Hummers' method was used to synthesis of graphene oxide sheet structure which acted as the stabilizer to fabricate polystyrene/graphene-based composite emulsion through Pickering emulsion polymerization.The overall synthetic procedure and research results as followed:A series of graphene oxide(GO)have been successfully fabricated utilizing the modified Hummers' method by graphite as raw materials and concentrated sulfuric acid as oxidizing agent.Results showed that the graphene oxide water dispersion was successfully synthetized through the Fourier transform infrared spectra(FT-IR),Ultraviolet(UV-vis),X-ray diffraction(XRD),Raman and thermogravimetric(TG).The microstructure of graphenee oxide can be observed by the transmission electron microscope(TEM)and scanning electron microscope(SEM),which is layer structure can be stripped easily.The effect of GO concentration on the stability of water dispersion was revealed via dynamic mechanical light scattering instrument(DLS).The charge intensity is getting stronger with the increasing of GO concentration range from 2mg/mL to 5mg/mL,indicating that water dispersion is more and more stable.Meanwhile the dispersion of graphene in different organic solvents was explored.Results showed that the graphene oxide is uniformly dispersed in water.The contact angle was less than 90°,which proved the hydrophilicity of graphene oxide was improved.The polystyrene/graphene oxide nanocomposite emulsion was synthesized via Pickering emulsion polymerization.Through the results of TEM,SEM and XRD,one can easily find that GO-stabilized PSt colloidal particles has been successful synthesized.The average particle size(200-300nm)of the composite emulsion decreased with GO concentration and the emulsions tended to achieve good stability at GO content were 20mg.The GO layer was wrapped on the surface of PSt microspheres to form a coating structure under the condition of microscopic.Compared with PSt homopolymer,the composites had excellent thermal stability which with initial decomposition temperature was delayed from 153? to 385? and the glass transition temperature dropped to 78.8?.The dynamics characteristic of the composite emulsion was investigated.Result indicated that conversion rate is increasing with the rasing with GO content.In the reaction,graphene oxide is not only being used as an effective solid stabilizer for Pickering emulsion,but also dispersed homogeneously into the production of polystyrene as a highly effective nanofiller.The polystyrene/reduced graphene oxide(PSt/rGO)nanocomposites are prepared in situ reduction of PSt/GO composite emulsion with hydrazine hydrate acted as reductant.The successful synthesis of composite was proved by Fourier transform infrared spectra(FT-IR),Raman,and X-ray diffraction(XRD).The effect of different GO content and hydrazine hydrate on the stability of the composite emulsion was explored.Results indicated that emulsion had good dispersibility and stability at the hydrazine hydrate content was 1mL.By means of SEM and TEM,the microstructure of the rGO sheet and PSt microspheres was characterized.The result of TG and DSC showed that the thermal stability and conductive properties of PSt/rGO composite emulsion are improved.The electrical conductivity of the samples were characterized by conductivity meter.The result of measurement showed that the conductive performance of GO and PSt/GO is poorer than that PSt/rGO composite emulsion.The electrical conductivity of the PSt/rGO composite emulsion was increased after reduction with hydrazine hydrate.The reduction made oxygen-containing groups disappeared and lamella structure more neat.The migration effect of the defects on the current carrying electrons was reduced.Thus,the conductive performance of PSt/rGO composite emulsion was improved to some extend.This research paves the way for the fabrication of graphene-based composite materials with novel nanostructures and microstructures.