Electrospun meaning.The most critical factor in controlling the structural morphology of the nanofiber structure is the viscosity of the polymer solution, a parameter that is directly related to the concentration of the polymer solution. In order to form fibers, the viscosity of the polymer must be within a certain range depending on the type of polymer and the solvent used. Zeng J et al., to prepare PLA nanofibers, different concentrations or viscosities are used from 1 to 5 wt% as shown in Figure 4, from ratios below 3% for beads or beaded fibers and 3% and higher for nanofiber beads [32].
Electrospun meaning
Below this area, a bead containing the nanofiber structure was formed. Spherical spheres were elongated and transformed into spindle-shaped spheres by viscosity, and the number of spheres in the structure decreased. Similarly, Liu et al. also reported a different specific viscosity range for the formation of uniform cellulose nanofibers [33]. In more recent studies, Deitzel et al [34] and Demir et al [35] have shown that a more viscous polymer solution can also form larger fibers. In summary, these studies have proven that there is an optimal value of polymer specific viscosity for electrospinning.
According to Sill and von Rekum [36], the concentration of the polymer determines the spinnability of the solution. For chain entanglement to occur, the solution must have a sufficiently high polymer concentration. However, the solution should not be too dilute or too thick. Solution viscosity and surface tension are affected by polymer concentration.
Electrospun nanofibers meaning
The carrying capacity of high conductivity polymer solutions is higher than that of low conductivity solutions. Therefore, the fibrous sheet made from a highly conductive solution exhibits higher tensile strength when subjected to an applied stress. By observation, increasing the conductivity of the solution results in a significant reduction in the diameter of the nanofibers. And it is also evident that the beam radius of the nanofiber is inversely proportional to the square root of the electric conductivity of the solution.
The conductivity of a given cell is related to the molar conductivity of the next. (6) [39], where k is the conductivity in mS/cm, c is the ion concentration in mol/L and therefore the molar conductivity (Λ) has the unit S cm2/mol.
Chitral and Shesha [40] published the results of an extensive study on the effects of modifying the conductivity of polyethylene oxide (PEO)/water solution on the electrospinning process and fiber morphology. The conductive effects of the PEO solution on the beam and beam path add NaCl to the solution and cause protrusions on the surface of the fibers as shown in Figure 5. The effects of the conductivity of the polyethylene oxide (PEO) solution in the beam and in the beam path are also considered here.
Electrospun scaffolds meaning
Zong et al. [37] conducted a study to observe the effect of adding various salts to poly(L-lactic acid) (PLLA) solutions in the electrospinning process. KH2PO4, NaH2PO4 and NaCl were assayed and each added separately to 1% w/v PLLA solutions. The resulting electrospun nanofibers were smooth, beadless, and also had smaller diameters than the electrospun nanofibers obtained from salt-free solutions. The KH2PO4 solution produced the largest diameter nanofibers, while the NaCl solution produced the smallest diameter nanofibers. It was found that the size of the ions also determines the diameter of the nanofibers. Ions with smaller radii had higher charge density and therefore resulted in higher stretch forces in electrospun nanofibers [41].
The molecular weight of the polymer also has a major impact on the morphology of the electrospun fibers. The entanglement of polymer chains in solutions, i. H. Solution viscosity essentially reflects molecular weight. By keeping the concentration constant and lowering the molecular weight, the polymer has the ability to form granules rather than smooth fibers. Smooth fibers are obtained by increasing the molecular weight. It should also be noted that very high molecular weights lead to the formation of microbands even at low concentrations [42, 43]. Cigdem A et al. [44] studied the effect of molecular weight (MW) on the structure of electrospun poly(vinyl alcohol) (PVA) fibers with molecular weights ranging from 89,000 to 186,000 g/mol when dissolved in water.