Surface Modification And Disaggregation Of Nanodiamond

Nanodiamond（ND）is a kind of important carbon nanomaterials,which not only has the basic characteristics of nanomaterials,such as small size effect,quantum size effect,macroscopic quantum tunneling effect and surface and interface effect,but also has inherent basic characteristics of the diamond itself such as high hardness,high thermal conductivity,good chemical stability,et al.Therefore ND has been widely applied.However,due to the large specific surface area and the special structure of ND,raw ND particles generally tend to aggregate and often form sub-micron or even micron grade reunion cluster,which makes it lose the unique function of the nanoparticles and greatly limits its application scope.In addition,surface functional groups of ND is single.Therefore,it is of great importance to disperse the ND particles and carry on the surface functionalization.In this study,we report two new and efficient chemical grafting methods for covalently linking the hydrophobic polymers and biocompatibility copolymer to the surface of ND to achieve the goal of functionalization and disaggregation of ND,shown in the following two parts:（1）Functionalization of ND with hydrophobic polymers via“grafting from”Firstly,ND particles were chemically oxidized with mixed acid.Thionyl chloride and ethylene glycol were utilized to react with oxidized ND to yield hydroxyl groups on ND surface.Then,the generated hydroxyl groups were converted into vinyl by a treatment with acryloyl chloride.These acryloyl chloride modified ND particles were further functionalized with vinyl monomers by in situ copolymerization with the initiator benzoyl peroxide（BPO）.The functionalized ND particles with hydrophobic polymers possess smaller size and more stable dispersion.（2）Functionalization of ND with biocompatibility copolymer via“grafting to”Under inert gas protection,with polyethylene glycol（PEG）and stannous caprylate（Sn（Oct）₂）as the initiator,PCL-PEG-PCL copolymer was synthesized successfully byε-CL monomer ring opening polymerization.ND particles were chemically modified with mixed acid and HDI,which introduce some isocyanates on the surface of ND.Then,the copolymer of PCL-PEG-PCL was grafted to the surface of ND by the reaction between isocyanate group and hydroxyl via“grafting to”method.The method improves ND dispersion and its biocompatibility.