Study On Preparation And Characterization Of Poly((Butelene) Terephthalate)/Regenerated Silk Fibroin Electrospun Mats

Poly (butylene terephthalate)(PBT) has good mechanical properties, lower price and nice processibility. The PBT melt-blown nonwovens have been widely used in biomechanical field such as blood filter. The PBT electrospun nanofiber membrane has high specific surface, small pore size and high porosity. However, the poor surface wettability limits the use of PBT due to its hydrophobicity. SF (Silk fibroin) is a natural polymeric material with good hydrophilic property, biocompatibility, biodegradability and so on. Therefore, it is a feasible way to blend PBT with SF using electrospinning method to combine the advantages of the two materials. In this paper, the RSF (Regenerated silk fibroin) was dissolved in DCM/TFA, and its electrospinning process parameters and the characteristics of nanofiber mats were studied. Moreover, RSF solution was blended with PBT solution to obtain RSF/PBT electrospun mats and then their properties were evaluated.The main work and results were listed as follows:First, The RSF was dissolved respectively in mixed solvent (DCM/TFA,1/1V/V) and formic acid(FA) to prepare the solution for electrospinning. The surface microscopic morphology of the nanofiber membrane, the molecular conformation of SF and its crystalline structures was characterized by SEM (Scanning electron microscopy), FTIR (Fourier transform infrared) and XRD (X-ray diffraction). The result showed that the optimum electrospinning concentration was16wt.%, and the optimum electrospinning voltage was20-23kV when the solvent was DCM/TFA; the distance was13cm between the needle tip and collector; the feed rate was0.5ml/h. The diameter of the nanofier was in the range of268-321nm under this condition. The diameter was more finer using formic acid compared with the mixed solvent while it showed little diversity when the concentrate was16wt.%. The molecular conformation of RSF was random coil or α-helix in RSF; while that of RSF electrospun nanofibers from RSF in DCM/TFA solution and FA solution were both mainly as random coil. For crystalline structures as the XRD showed, it was silk Ⅰ in RSF and both amorphous in RSF electrospun nanofiber from RSF in DCM/TFA solution and FA solution.The conclusion could be obtained that DCM/TFA could also be used as the solvents of RSF as its traditional spinning solvent like FA.Secondly, RSF solution and PBT solution were mixed with different ratios using the same solvent DCM/TFA. Characterizations, including SEM, FTIR, contact angle, dissolution rate and so on were used to investigate morphology, molecular conformation, surface wettability and dissolution property. The result showed that the two solutions were well compatible and the nanofiber of each ratio showed distinct fiber morphology with a diameter of204-321nm. As the electrospinning voltage increased, the diameter decreased and the standard deviation increased after the first reduce when the blending ratio was50/50, the optimum voltage was22kV. The result of FTIR indicated that the molecular conformation of RSF in the blended nanofiber membrane was random coil or α-helix. Conclusions could be drew from the contact angle and dissolution rate that with the increase of RSF, the wettability of the nanofber membrane was improved but the dissolution rate increased at the same time:the pure RSF electrospun membrane and the blended membrane of80/20were hydrophilic materials which could be completely infiltrated with low dissolution rate; the pure PBT electrospun membrane and the blended membrane of20/80were hydrophobic materials which can’t be infiltrated and had high dissolution rate that is higher than50%; the blended mats of50/50could be infiltrated but with a long time and its dissolution rate was14.3%. The average pore size of14wt.%RSF electrospun mats and blended mats of80/20and50/50were1.62-2.16μm.Finally, the methanol treatment method was introduced into the pure RSF electrospun nanofiber membrane and blended nanofiber membranes of80/20,50/50in order to improve the dissolution property of the nanofiber membrane when the content of RSF was high. The various performance after methanol treatment were characterized by SEM, FTIR, XRD, contact angle and dissolution rate. The results showed that, after the methanol treatment, the fibers aligned more closely and the diameter increased; the molecular conformation transformed from α-helix and random coil to β-sheet; the crystalline structures transformed into silk Ⅱ and the crystallization degree improved; the wettability of the nanofiber membrane was also extraordinary and the dissolution rate decreased apparently which was about8%-16%.