Research On Fabrication And Mechanism Of Polymer Bone Scaffold Reinforced By Two-Dimensional Nanosheets

Two-dimensional（2D）nanosheets,such as graphene oxide and molybdenum disulfide and so on,have great potential in enhancing mechanical properties of polymer scaffolds due to their ultrathin sheet structure and excellent mechanical properties.However,the agglomerations of 2D nanosheets takes place spontaneously due to large specific surface area,high surface energy and strong van der waals forces,which restricts their effect of enhancing the mechanical properties of polymer scaffolds.In this paper,3-aminopropyl triethoxysilane（APTES）was introduced to modify GO nanosheets via surface modification method.Nano-diamond（ND）particles were used to physically intercalate into MoS₂nanosheets.MoS₂nanosheets were uniformly in situ grown on the surface of GO nanosheets via the hydrothermal method.The dispersibility of 2D nanosheets in polymer was improved via these methods.What’s more,selective laser sintering（SLS）was also used to fabricate polymer composite bone scaffolds,and the mechanical and biological properties of the scaffolds were also discussed.The main work and innovations of the paper are as follows:1.GO was modified with 3-aminopropyl triethoxysilane（APTES）to facilitate its dispersion in polyglycolide（PGA）scaffold and improve interfacial bonding between GO nanosheets and PGA matrix.It could be found that the silanol groups of APTES could be combined with the hydroxyl and carboxyl groups of GO nanosheets by covalent bond,thus attaching onto the surface of GO nanosheets to introduce a large number of long alkane chains and amino groups.Among them,the long alkane chains could support the GO nanosheets and prevent the agglomerations of GO nanosheets.At the same time,the amino groups could be bonded with the carboxyl groups of PGA.In this way,APTES acted as a bridge to connect GO and PGA matrix,enhancing the interface bonding effect.2.The physical intercalation of nano-diamond（ND）particles was used to embed into MoS₂nanosheets,promoting the dispersion of MoS₂nanosheets in poly（3-hydroxybutyrate-co-3-hydroxyvalerate）（PHBV）scaffold.It could be found that MoS₂nanosheets had typical sheet structure while ND particles possessed octahedral spherical structure.ND particles could be embedded into the adjacent MoS₂nanosheets by means of ultrasonic dispersion and magnetic agitation,forming the“sphere sheet surrounding structure”.Then the sandwich effect of ND particles could prevent the restacking of MoS₂nanosheets and improve their dispersion in the polymer matrix.In addition,MoS₂nanosheets with large transverse dimensions could also prevent the aggregations of ND particles.3.MoS₂nanosheets were in situ synthesized uniformly on the surface of GO nanosheets with the help of a cetyltrimethylammonium bromide（CTAB）-assisted hydrothermal process to facilitate their dispersion in polylactic acid（PLLA）scaffold.Find out the specific mechanism:The positively charged quaternary ammonium ion of CTAB could combine with the negatively charged carboxyl and hydroxyl groups of GO through electrostatic action,so as to attach onto the GO nanosheets and endow GO positive charge.So that Mo O₄^2-could be adsorbed on the GO nanosheets.And then L-cysteine was added to act as not only sulfur source,but also reducing agent.Finally,the+6 Mo could be reduced to+4 Mo,and then MoS₂nanosheets gradually nucleated and grew.It could be found that MoS₂nanosheets grew selectively and uniformly on the surface of GO nanosheets.Moreover,the newly generated MoS₂nanosheets could produce steric hindriance effect and prevent the restacking of GO nanosheets,improving the dispersibility of them in the polymer and enhancing the mechanical properties of polymer scaffold.It was also found that the mechanical strengthening mechanism mainly included crack deflection,crack bridging,crack pinning and pulling out of GO/MoS₂.4.The influence of these three methods on mechanical properties was comprehensively studied,and comparative analysis was conducted.It was found that the tensile modulus of the composite scaffold after APTES modification of GO increased by 28%.And the tensile modulus of the composite scaffold after ND particle intercalation of MoS₂nanosheets increased by 48%compared with that of the pure MoS₂nanosheets composite scaffold.The tensile modulus of the composite scaffold after in situ growth of MoS₂nanosheets on GO was increased by 56%,indicating that the in situ growth technique had the best mechanical enhancement effect on the scaffold.The tensile strength test result showed that the tensile strength of the composite scaffold after in situ growth of nanosheets is 10.2 MPa,which is 34.2%and 41.7%higher than that of the scaffold added nanosheets separately.This is because the in situ growth technology can realize the selective distribution of newly grown nanomaterials,which can support the dispersion of substrate material via the formation of the steric hindrance effect,promoting their dispersion in polymer matrix.What’s more,two kinds of nanomaterials can be chemically bonded,which improves the compatibility of them,resulting in increased stress transfer efficiency and energy dissipation.Figures:42,Tables:2,References:112...