Functionalization Of Graphene Oxide And Its Application In Nanofibers

Graphene has attracted enormous attention for its unique physical and chemical properties since it was discovered.Graphene sheets tend to agglomerate irreversibly because of the Van der Waals force and ?-?interaction among sheets.However,the unique properties of graphene are relevant to the single layer state of graphene.Exfoliating graphene fully is essential for its application.Graphene and its functional derivatives are usually used as nanofillers for polymers matrix.According to those previous relevant literatures,the performances of polymers matrix were improved apparently.In this paper,three parts are included: First,the functionalization of graphene and its derivatives' dispersibility in various solutions are researched;Second,enhancing mechanical properties of polyelectrolyte complex nanofibers with graphene oxide nanofillers pretreated by polycation;Third,the effects of graphene oxide functionalized by Ag nanoparticles on the performances of polyelectrolyte complexes nanofibers.In part one,three approaches of functionalization of graphene have been described in detail.For improving the dispersibility of graphene in water,graphene was functionalized by hyperbranched polyglycerol.Substantial amount of groups containing oxygen on the surface of graphene was used to initiate the ring-opening polymerization of glycerol in situ on graphene flat at 140 ?.Ascribing to the abundant of hydrophilic groups,such as –OH,C-O-C et al,in the hyperbranched polyglycerol molecular structure,the result product shows excellent water-solubility and can keep dispersing well over three months.Considering the requirement of part two,the dispersibility of graphene oxide in 90 wt% acetic acid need to be researched.The solution is described as follow: negatively charged graphene oxide interacts with positively charged chitosan molecular chains which caused by the protonation of –NH2 in 90 wt% acetic acid.Between chitosan andgraphene oxide,there exists strong synergy effect of electrostatic attraction force and hydrogen bonding force.Therefore,graphene was covered by chitosan layers.With the aid of the protonation of –NH3 in chitosan molecular structure,the nanocomposite can be dispersed in 90wt% acetic acid.At last,for the purpose of application of graphene oxide functionalized by Ag nanoparticles,the dispersibility of the nanocomposite in H2 O,acetic acid(90 wt%),N,N – dimethylformamide(DMF)was researched.The results shows that the nanocomposite will reversibly agglomerate in the above solutions.In part two,chitosan/gelatin(CS/GE)was chosen as the modal polyelectrolyte complex(PEC)for the research of the mechanical enhancement of polyelectrolyte complex using GO as nanofiller.As the results show that: At 1.5 wt% filler content,GO/CS/GE nanofiber membranes achieved 340% augment of mechanical strength,175%improvement of Young's modulus and 460% boost of toughness compared with neat CS/GE,which were attributed to effective filler-matrix interactions and stress transfer.In part three,the effects of using GO functionalized by Ag nanoparticles(GO-AgNPs)as the nanofiller on the antibacterial and mechanical properties of CS/GE PEC matrix have been researched.As the results show that: At 1.5 wt% filler content,GO-AgNPs/CS/GE nanofiber membranes achieved 2.14 times and 1.13 times augment of inhibition zone diameter,15 days of Ag+ release time and 90% of Ag+release dosage,413% improvement of Young's modulus and 254% boost of tensile strength,3.39 times of weight increase after immersed in phosphate buffered saline(PBS,pH=7.4)for 30 min compared with neat CS/GE.