Construction Of Hydrogel Of Graphene-based Nanocomposite

Nanocomposite hydrogels are formed by inorganic nanoparticles(NPS)as crosslinking agents.They combine the novel properties of nanoparticles with unique properties of hydrogels which lead to new functions originated from the synergic effect or complementary performance of components.Such nanocomposite hydrogels have attracted interests in many field such as drug delivery,catalysisi and biomaterials.As a new member of the family of carbon nanomaterials,graphene is widely regarded as a revolutionary new material,which has already attracted enormous interest due to its unique properties.However,graphene can not be directly used in the preparation of hydrogels because of the inherent hydrophobic properties of graphene and the weak interfacial binding capacity between polymers and graphene.The use of graphene(GO)is an effective strategy to avoid the hydrophobicity of graphene,but GO has serious damage to the structure and properties of graphene,especially conductive and thermal conductivity.Based on the above considerations,in order to achieve the goal of preparation of high performance graphene-based nanocopposite hydrogel(GNH),the commercial water-soluble initiators were chemically grafted onto the original graphene surface(initiator-g-graphene,I-g-G),and then free radical polymerization was initiated by I-g-G in situ preparation of GNH.During the specific research schemes,First,by diazonium salt reaction,the P-aminophenylethanol was successfully grafted onto the surface of the original graphene(G-OH).Then in order to increase the grafting amount of alcoholic hydroxyl groups on the basis of no more damage to the structure and properties of graphene,we synthesized G-M-OH based on G-OH and G-ACVA was synthesized by grafting water-soluble initiator-4,4-azobis(cyanovaleric acid)(ACVA)onto G-M-OH by esterification reaction.The study of conductivity and water solubility of G-ACVA showed that G-ACVA inherited the inherent structure and properties of the original graphene to a great extent due to the controllable properties of the grafting reaction.When the grafting amount of ACVA was 13.62 wt%,The volume conductivity of G-ACVA is 2900 S.m-1(5x104 S.m-1 for the original graphene).And G-ACVA has excellent water solubility(saturated aqueous dispersion concentration of 1.9 mg.ml-1),which is suitable for initiating free radical polymerization of water-soluble monomers such as N,N-dimethylacrylamide(DMAA).Finally,graphene/PDMAA nanocomposite hydrogels was synthesized in situ in the present of G-ACVA.The results showed that compared with PDMAA hydrogel and GR/PDMAA nanocomposite hydrogel,the mechanical properties of G-ACVA/PDMAA nanocomposite hydrogel are obviously improved.The compressive strength can reach 813 kPa and the tensile strength reaches 32.1 k Pa.And the addition of graphene imparts better conductivity to the hydrogel.With the increase of the amount of G-ACVA,the conductivity of G-ACVA/PDMAA nanocomposite hydrogel increases,and when the amount of G-ACVA is 1.09 wt%,the conductivity reaches a maximum of 1.58 m S/cm.In short,this work presents a hydrophilic surface modified I-g-G with the function of both initiator and crosslinker,and then GNH has been prepared in situ through radical polymerization.This material design and preparation of graphene and its composite hydrogels at the molecular level are not only promising to further explore the potential of graphene,but also to further enrich the content of basic research of Materials Science.