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Preparation And Properties Of Functionalized-Graphene/Poly(Lactic Acid) Nanocomposite

Posted on:2017-08-03Degree:MasterType:Thesis
Country:ChinaCandidate:W P Y GuoFull Text:PDF
GTID:2311330488477704Subject:Chemistry
Abstract/Summary:PDF Full Text Request
Graphene as a novel two-dimensional one-atom-thick materials has become a hotspot in the fields of scientific research and industry. Because of its excellent mechanical, optical, electrical and thermal properties, Graphene has been used as a nanofiller to prepare polymer nanocomposites. Even adding a small amount of graphene, the physical properties of the polymer matrix can be improved significantly.However, the optimal performance can not be achieved without the homogeneous dispersion of nanofillers and strong interfacial adhesion between nanofillers and polymer matrix. Owing to the large specific surface area and stronginterlayer van der Waals force of graphene layers, it is difficult to disperse in the polymer, and thus, it is inevitable to tune the surface properties of graphene. Polylactic acid(PLA), as a biodegradable and biocompatible polymer, has been widely used in drug dilevery, tissue engineering and many other medical fields. However, its poor mechanical performance, slow crystallization rate, low crystallinity and brittleness have greatly limit its further application.In this work, we aimed to high strength PLLA/graphene composites, and solve the poor mechenical properties of PLLA and aggregation of graphene layers. Firstly, PLLA functionalized graphene was prepared via the in situ polymerization of L-lactic acid, and then properties of functionalized graphene/PLLA composites prepared via solvent mixing method was investigated. In the end, functionalized graphene/PLLA nanofiblerwas prepared via electrospinning method, and the potential application in tissue engineering scaffolds was also discussed. The main content and results are as following:(1) A simple method was proposed to modified graphene. Firstly, graphene oxide(GO)was synthesized from commercial graphite powder according to a modified Hummer's method. Furthermore, PLLA grafted GO(GO-g-PLLA) was obtained via in situ polycondensation of GO and L- lactic acid at 120 ?. The structure of GO-g-PLLA was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopic and thermogravimetric analysis. The dispersion test shows that the GO-g-PLLA can uniformly dispersed in the organic solvent.(2) GO-g-PLLA/PLLA nanocomposites were prepared by solution blending. The tensile test, scanning electron microscopy, differential scanning calorimeter, polarized opticalmicroscope, X-ray diffraction were used to investigate the properties of composite materials. The results show that GO-g-PLLAcan disperse well in the PLLA matrix. Tensile strength of composite materials are higher than that of PLLA, when the filler content is 3.0 wt %, the tensile strength reached 60 MPa. The GO-g-PLLA filler can promote the mobile of PLLA chains, and works as nucleation agent to promote the crystallization of PLLA. In addition, the GO-g-PLLA do not change the crystal type and crystallization mechanism of PLLA.(3) A series of GO-g-PLLA/PLLA nanofibers were prepared by electrospinning method. The physical and chemical properties of the composite were studied byscanning electron microscopy, transmission electron microscopy, contact angle test, tensile test, differential scanning test, thermogravimetric analysis. Results show that nanofibers have a certain orientation and GO-g-PLLA can evenly dispersed in the nanofibers. GO-g-PLLA can improve strength and toughness of PLLA, when the content was 1.0 wt %, the tensile strength was 6.5 MPa. The crystallization properties and thermal stability performance also improved in composite. Compared with PLLA, the composite have better hydrophilic surface, biological properties and degradability properties The above results show that the GO-g-PLLA/PLLA nanofibers have good mechanical properties, crystallization properties, thermal stability, biological activity, degradability properties and may have potential application in tissue engineering.
Keywords/Search Tags:graphene, PLLA, covalent modification, In-situ polymerization, composite, mechanical properties, thermal performance, electrospinning, tissueengineering
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