Preparation Of Graphene By Liquid-Phase Exfoliation With Dispersing Stabilizer

Owing to processing excellent thermal,electrical properties,outstanding physical property,graphene,a new member of the carbon material family,has a very wide application prospects especially in the fields of semiconductor,sensor,energy storage and polymer composites et al.With the research development of graphene,more and more attentions are paid on graphene production.Production of graphene with high-quality and lost-cost is the key issue of future development.Liquid-phase exfoliation method with graphite as raw material,is capable of mass producing high-quality graphene.Even more,dispersant/stabilizer assisted liquid-phase exfoliation method can produce graphene with higher stability and more choices of solvents.In our work,graphene were prepared using two pyrene-containing polymers as dispersants by liquid-phase exfoliation method.During the process,the exfoliation force was provided by high shear mixer instead of ultrasonication.Our method has the following advantages:First,production of graphene with high shear mixer has higher output and stability,the structure defect of graphene obtained by the shear-exfoliation method is lower than the conventional ultrasonic-exfoliation method.Second,with the existence of the pyrene-containing dispersing stabilizers,exfoliation can be carried out in water and low-boiling point solvents.On the contrary,ordinary LPE solvents such as NMP,DMF are expensive and difficult to evaporate.Third,the stabilizer can improve the dispersing quality of graphene in solvents and following polymer matrix.With these points in mind,the thesis work is carried out from three aspects:1)molecular design and synthesis of two dispersants:oil-soluble pyrene-terminated polystyrene(PyPS)and water-soluble pyrene-containing copolymer(PyP-co-M);2)production of graphene by dispersant assisted Liquid-phase exfoliation(in chloroform and water respectively);3)The application of the graphene was preliminary explored.Obtained results are as follows:1)Pyrene-containing dispersants suitable for water and chloroform system have been successfully synthesized.2)In the presence of dispersants of PyPS and PyP-co-M,graphene can be produced by LPE method in chloroform(a low boiling point and poor solvent for common LPE)and water respectively.The optimal parameters are listed as following:A)PyPS concentrations=0.7 mg/mL,initial graphite concentrations=30 mg/mL,exfoliation time=210min(chloroform system)B)PyP-co-M concentration=2 mg/m L,initial graphite concentrations=50 mg/mL,exfoliation time=280 min(water system)3)The obtained graphene flakes have fewer structural defects shown from AFM and TEM pictures,and the flakes are about 400 nm in size,1-3 in layer respectively.4)In the presence of PyPS,thermal conductivity of PS-based composite increased by 1.38 times,and electrical conductivity reached 0.00814 S/m with 3.0 wt%graphene.The tensile strength of composite reaches 38.67±1.12 Mpa with 1.0 wt%graphene.5)Film which was prepared by filtering graphene had conductivity of 4×10~4 S/m.Graphene-based hydrogel had good compression performance,and conductivity can reach 1.06 S/m with 0.4 wt%graphene.In summary,two pyrene-containing dispersing stabilizers were successfully synthesized.With the above-mentioned dispersants,high-quality graphene can be produced by a high shear mixer in chloroform and water systems cheaply and environmental-friendly.This method provides a new option for graphene preparation and the graphene obtained by this method has a broader application prospects.