Construction And Modification Of Functional Fibers And Its Application In Biomedical And Catalytic Fields

With the development of manufacturing industry and the progress in science and technology,the demand for functional fibers in various application fields is increasing,thus multi-technical methods are required to perform specific functional design of fibers.Electrospun fibers have the advantages of high aspect ratio,3D nano-structure,large specific surface area,and high porosity etc.,they have been widely used in the fields of filtration,catalysis,sensing,optoelectronic devices,and biomedical materials.Topology control and surface modification of electrospun fibers could enhance their functional performance.Based on the considerations mentioned above,we chose electrospun fibers as substrates to construct new functional fibers for biomedical applications and photocatalytic degradation of dyes,and the variations of fibers during the modification process were further characterized for studies of structure-activity relationship.The research work includes the following two parts:In this study,polycaprolactone（PCL）and typeⅠcollagen（COL）were electrospun to oriented nanofibrous mats,and layer-by-layer self-assembly（LBL）technique was then carried out to modify the mats with chitosan（CS）and COL molecules.ζ-potential,FT-IR analysis and XPS measurement indicated the successful fabrication and modification,and the variation of the oriented PCL/COL mats in LBL process was systematically studied by characterizing the surface morphology,wetting behavior and mechanical properties.The results demonstrated that the surface morphology was changed and the surface roughness was increased in LBL process,additionally,LBL-structured mats exhibited improved mechanical properties with the maximal tensile strength of 35.1±7.0 MPa and the best elongation of 106.0±11.5%.Moreover,cell experiments indicated the excellent biocompatibility of LBL-structured mats,and L929 fibroblasts and human umbilical vein endothelial cells showed oriented adhesion and growth along the direction of nanofiber arrangement.It was interesting that LBL modification could not affect the oriented growth,indicating that LBL-structured mats have considerably potential applications in the biomedical field.In this study,the combination of thermally induced phase separation and non-solvent phase separation mechanisms was used to prepare porous electrospun PCL fibrous mats by one-step electrospinning,but the PCL fibrous mats did not possess photocatalytic properties.Ti O₂,as a kind of traditional photocatalytic material,has been widely used in wastewater treatments due to its cost-efficiency,high stability and low toxicity,however,it could hardly be reused and might lead to secondary pollution.Therefore,porous electrospun PCL fibrous mats were used as carriers for the capacity and dispersion of Ti O₂.The porous PCL mats could provide large contact area for high photocatalytic efficiency of Ti O₂.Besides,the addition of rectorite（REC）could reduce the diameters of fibers and enlarge the specific surface area,which might be beneficial to photocatalysis.More importantly,REC played an important role in improving the function of porous PCL/Ti O₂ mats,which contributed to a high rate of photocatalytic degradation.The results indicated that porous PCL/Ti O₂/REC mats could serve as potentially excellent photocatalysts in the degradation of organic dyes.