The Study Of Nano-mechanics For Bio-degradable Polyester Fiber

In recent years,with the improvement of economy,people pay more attention to the surroundings and their own health.Biodegradable polyester materials are favored by materials scientists and physicians because of their excellent bio-compatibility and bio-degradability.This type of polyester material with simple molecular structure and good mechanical properties is widely used in medical devices and medical implantable materials.However,due to the difference in molecular structure,there are differences among mechanical properties,and the long degradation cycle of polyester materials limits the scope of its application.People use modified methods to improve the performance of polyester materials,of which the simpler electrospinning technology is applied more frequently.Researches,found that the mechanical properties and degradation properties of the fiber membrane obtained by electrospinning have been improved.Over the years,the research on polyester fiber materials has become a hot topic.But these studies are all about the modification of the macro-mechanical properties of fiber materials,and few people have studied its internal mechanism at the micro-nano scale.In this paper,electrospinning technology is used to prepare polyester fiber membranes.With the aid of single-molecule force spectroscopy techniques based on atomic force microscopes,the intrinsic mechanical elastic behavior in the single molecular chain and the interaction between single chain molecules of bio-degradable polyester fiber membranes(PLA,PCL)Further,the effect of the internal intermolecular chain structure at the single-molecule level on the mechanical properties of macroscopic materials and the internal mechanism are revealed.The results shows that both PLA and PCL polyester fiber single chain can obtain their own intrinsic elasticity in nonane and are verified by QM-FRC and QM-WLC model respectively.Combining the intrinsic elasticity of PLA and PCL obtained by the research group before,it is found that there are significant differences between the intrinsic elasticity of PLA and PLA fibers but the same between PCL and PCL fiber due to the transformation of the molecular chain structure.Through the scanning electron microscopy results of the electrospinning fiber in the degradation process and fiber quality loss,the degradation of polyester fiber membrane prepared by electrospinning in acid,alkali and water is studied.It is found that the degradation of polyester fiber membranes under different circumstances is the same as that of polyester materials,namely: alkali > acid > water.However,the degradation rate of fiber membranes is faster than that of polyester materials in the same circumstance.This is because the polyester material is a partially crystalline polymer and the molecular chains in the crystalline region are packed very tightly,which limits the rate of degradation.Electrospinning increases the distance between the polyester fiber molecular chains,thereby the contact area of the polyester fiber is also increased.There are larger gaps between the polyester fibers.And because of the existence of side chain methyl branches in the PLA molecular structure,the hydrophobicity of PLA is caused.Therefore,the degradation rate of PCL fiber membrane is faster than that of PLA fiber membrane.