| Particularly, nanodiamond(ND) has recently received considerable attention since the discovery by Russian researchers who explored the composition of residues from detonations in closed containers in the 1960 s. And its favorable properties such as rather easy availability, biocompatibility, low toxicity and wear-resisting property make it a promising material for various applications.Nevertheless, due to the large specific surface area, the remaining graphitic soot, the intrinsic van der Waals forces and the chemical bonds among the surface functional groups, raw ND particles generally tend to aggregate and form poor dispersions. The ND agglomerates can not provide any property improvement; instead they act rather as defects and often result in degradation of mechanical properties. Therefore, critical challenges lie in dispersing the ND particles individually and to be able to assess the potential of this material in various applications.In this study, we report two new and efficient methods for covalently linking the biopolymer and epoxy resin to ND, shown in the following two parts:(1) Functionalization of nanodiamond with biopolyesterND particles were first added into a solution of strong oxidizing acid. The generated carboxyl groups were next converted into hydroxyl groups by a treatment with thionyl chlorides and 1,6-hexanediol. Then, the hydroxyl group-functionalized ND was grafted with L-lactide, ε-caprolactone or methylcarbonate to form ND-graft-PLLA(ND-g-PLLA), ND-graft-PCL(ND-g-PCL) or ND-graft-PTMC(ND-g-PTMC). The hybrids of biopolymer-grafted ND may simultaneously optimize the ND dispersion and improve the biocompatibility. What’s more, it may promise multipurpose applications in biomedical systems as bionanomaterials.(2) Functionalization of nanodiamond with four kinds of epoxiesIn this study, we report a simple and effective method for covalently linking the epoxy to the surface of ND. The method was to chemically oxidize with a mixture of nitric acid(ND-COOH), and then converted the carboxyl groups next into amine groups by a treatment with thionyl chloride and triethylenetetramine(TETA)(ND-NH2). Then, the functionalized ND particles were grafted with different epoxies, respectively. Along with the well-known bifunctional diglycidyl ether of bisphenol-A(DGEBA), three epoxies of high-functionality, namely the trifunctional triglycidyl p-amino phenol(TGAP), the tetrafunctional tetraglycidyldiamino diphenylmethane(TGDDM) and the bisphenol-A novolac epoxy resin(BAEPN) have been investigated. The epoxy-grafted ND may optimize the ND dispersion and it is also ideally suited to react with these groups of various polymers, such as polyamide, polyurethane, polyacrylic acid, polyvinyl alcohol, etc. Thus, the epoxy-grafted ND may optimize the ND dispersion and it plays an important role as rigid crosslinker or chain extender to improve the interfacial adhesion between ND fillers and polymer matrices. |
