Preparation And Properties Of Electrospun Polylactic Acid-based Shape Memory Composite Materials

In recent years,shape memory polymers(SMPs)have been widely used in medical,aerospace,textile and other fields due to its characteristics of memory,large shape variation,easy to process and shape,and wide source.However,the research on shape memory polymers mainly focuses on the structure design and application of macroscopically large size,while the research on the micro-nano-size devices in the initial stage is relatively less,and the mechanical properties of shape memory polymer are not ideal.With the development of intelligent structure and manufacturing technology,nanomaterials with porous structure such as fiber and foam will play a key role in drug release,tissue engineering and interventional therapy.In addition,shape memory fibers or thin film materials also have important applications in smart clothes.Therefore,improving the mechanical properties of shape memory polymers and exploring the development of micro-nanostructured shape memory polymers are the keys to obtain high-performance shape memory polymers.In this paper,two kinds of thermally induced shape memory composite films were prepared by using polylactic acid as matrix material by adding different fillers and adopting electrostatic spinning technology.The main research contents and results are as follows:The first part,sisal nanocellulose crystallites was prepared with sisal as raw material through dewaxing,alkaline boiling and hydrolysis,followed by silanization and amidation treatment on its surface.Then the nanocellulose grafted with hyperbranched polylactic acid(H-PLA-CNCs)was prepared by grafting hyperbranched polylactic acid on the surface.Lastly,PLA/H-PLA-CNCs composite films was prepared by electrostatic spinning through adding H-PLA-CNCs to the polylactic acid solution according to different concentration ratios.The results show that the PLA/H-PLA-CNCs composite film performs well on its own mechanical properties and can achieve a tensile level and a fracture degree of 13.11 MPa and32.5%,respectively.When the content of H-PLA-CNCs was 5 wt.%,the shape recovery rate of the composite membrane was as high as 93%,which was 37% higher than that of the pure PLA membrane(56%).After five cycles,the shape recovery rate of the composite film only reduced by 5%.The second part,perylene imide derivatives with carboxyl terminus(PBI)with carboxyl terminal groups were synthesized mainly by amidation reaction.Thenperylene imide derivatives with carboxyl terminus(PBI-GNs)was prepared by stacking PBI with graphene ?-? in a certain proportion.Lastly,the PLA/PBI-GNs composite membrane was prepared by electrospinning the prepared PBI-GNs into polylactic acid solution.The microstructure,morphology and performance of PLA/PBI-GNs composite membrane were analyzed by means of SEM,TGA,DSC and DMA.It was finally found that if the amount of PBI-GNs added was 9 wt.%,the elongation at break and tensile strength of the composite film could reach 25.63% and21.23 MPa,respectively,which increased by 346% and 11.13% compared with the pure PLA film.The shape memory recovery rate of the composite membrane reached the maximum value of 92.3%,which was 36.3% higher than that of the pure PLA nanofiber membrane,and only reduced by 3.7% after five cycles.