Preparation And Properties Optimization Of Graphene Oxide/Polylactic Acid Composites

Bone fracture and other orthopaedic diseases may bring inconvenience and great pain to patients.Demand for clinical artificial bone fixation and repair materials is rising and higher requests have been raised.Ideal artificial bone materials should not only have good biocompatibility and osteoinductivity,but also should have suitable strength and toughness matching with human bones,excellent wear-resisting property and surface wettability property.Polylactic acid?PLA?is a kind of biodegradable polymers that has been widely used in biomedical field.However,it's usually difficult for pure PLA to be used as artificial bone materials due to its single performance.Developing and preparing PLA based composites with high performance is the research focus and inevitable tendency.In this research work,graphene oxide?GO?was firstly prepared by modified Hummers method without use of NaNO₃,during which there were no harmful gases forming.There were many oxygen containing functional groups exsiting on its surface and edge.Results showed that those prepared GO sheet can be dispersed well in H₂O and dimethylformamide?DMF?for a long time.Secondly,nine films were prepared based on different organic solvents and drying temperatures.The one based on trichloromethane?CHCl₃?and dried under 30⁴0? appeared smooth and dense,residual solvent content of which was also the least.Then,suspension with GO in DMF and solution with PLA in CHCl₃ were mixed together.A series of GO/PLA films were prepared by solution stir,film spreading and drying.Results showed that weak hydrogen bonding interaction existed between GO sheets and PLA molecule chains.When GO content was 0.50wt% and 0.75wt%,the tensile strength and elongation at break were 65.3MPa and 17.3% respectively,which were both the maximum.The wear-resisting property of PLA were greatly improved by adding moderate GO and GO/PLA composite with 1wt% GO added owned the lowest friction coefficient and the least abrasion loss.When GO content was changed from 0wt% to 1wt%,the contact angle decreased from 80.824° to 68.072°,indicating that GO is beneficial to improve surface wettability property.However,it changed less obviously when GO content exceeded 1wt%.The opitimal GO content might be 1wt% after an overall consideration of influences that GO had on several related properties.Finally,polyethylene glycol?PEG?was added to blended solution when preparing GO/PLA composite with 1wt% GO content.Results showed hydrogen bonding interaction between different components was enhanced and the interface bonding force was stronger with PEG added.The tensile strength reduced with the increase of PEG content,but elongation at break increased.By using 4wt% PEG,the composite achieved best synthesis mechanical properties.The tensile strength was 54.9MPa,which has been improved 33.3% compared to pure PLA and the elongation at break was 19.6% which is 6.3 times of pure PLA.PEG also helped to further improve wear-resisting properties of GO/PLA composites and this optimizing effect came to a limit when PEG content reached 4wt%.When PEG content was changed from 0wt% to 8wt%,the contact angle decreased from 68.072° to 57.004°,indicating the surface wettability of GO/PLA composites being further improved.In addition,cell adhesion and proliferation results showed those GO/PLA composites with PEG as the compatibilizer owned good biocompatibility.