Core‐Sheath Structure in Electrospun Nanofibers from Polymer Blends

Abstract

Summary: Electrospinning of polymer blends offers the potential to prepare functional nanofibers for use in a variety of applications. This work focused on control of the internal morphology of nanofibers prepared by electrospinning polymer blends to obtain core‐sheath structures. Polybutadiene/polystyrene, poly(methylmethacrylate)/polystyrene, polybutadiene/poly(methylmethacrylate), polybutadiene/polycarbonate, polyaniline/polycarbonate, and poly(methylmethacrylate)/polycarbonate blends were electrospun from polymer solutions. It was found that the formation of core‐sheath structures depends on both thermodynamic and kinetic factors. Incompatibility and large solubility parameter difference of the two polymers is helpful for good phase separation, but not sufficient for the formation of core‐sheath structures. Kinetic factors, however, play a much more important role in the development of the nanofiber morphology. During the electrospinning process, the rapid solvent evaporation requires systems with high molecular mobility for the formation of core‐sheath structures. It was found that polymer blends with lower molecular weight tend to form core‐sheath structures rather than co‐continuous structures, as a result of their higher molecular mobility. Rheological factors also affect the internal phase morphology of nanofibers. It was observed the composition with higher viscosity was always located at the center and the composition with lower viscosity located outside.TEM image of electrospun polybutadiene/polycarbonate nanofibers at 25/75 wt.‐% ratio after staining by osmium tetroxide. The dark regions are polybutadiene and the light region is polycarbonate.magnified imageTEM image of electrospun polybutadiene/polycarbonate nanofibers at 25/75 wt.‐% ratio after staining by osmium tetroxide. The dark regions are polybutadiene and the light region is polycarbonate.

Large-scale organic nanowire lithography and electronics

“…S6b,c and Supplementary Note S2), a P3HT:PEO-blend NW has a coreshell structure along the wire axis. The origin of the core-shell structure of printed NW is explained by phase separation of polymer blends, which can be caused by the incompatibility or the large solubility parameter difference in solution 22 . On the basis of grazing-incidence X-ray diffraction (GIXRD) and polarized photoluminescence analysis for the aligned OSNWs, we found that the aligned NWs had long-range ordered nano-domains along the wire axis (Supplementary Figs S7 and S8, and Supplementary Notes S3 and S4).…”

Effects of drug solubility, state and loading on controlled release in bicomponent electrospun fibers

“…Lu has a lower molecular weight than PCL and higher molecular mobility and consequently it migrates to the regions of highest shear rate (at the walls of the needle). The higher viscosity component (PCL) occupies mostly the center of the fiber [40].…”

“…Multicomponent fibers can be obtained mainly by two techniques [5]: direct electrospinning of polymers solution (in a single-needle configuration, if a mixture of polymers is co-dissolved in the electrospinning solution or a multi-needle configuration in which the polymer solutions are separated in parallel or concentric syringes) and post-treatment of the single-component electrospun fibers (which can include coating with other inorganic-polymer layers [6,7], grafting [8], crosslinking [9], chemical vapour deposition [10], functionalization with other (bio)polymers [11]). In addition to the new physico-chemical properties that arise from using various components, a variety of fiber structures can be obtained such as core-shell fibers, micro/nanotubes, interpenetrating phase morphologies (matrix dispersed or co-continuous fibers) [12,13], nanoscale morphologies (spheres, rods, micelles, lamellae, vesicle tubules, and cylinders) [14] and multilayered constructs (either with different composition or different fiber diameter) [15,16].…”

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“…A similar result was also observed by Yang et al 16 . In general, the ability to form coaxial electrospun fibres with fine core-shell interface depends on both process parameters and solution properties 17,32 . In this work, the effects of solution properties (i.e., electrical conductivity of the core and shell solutions) Fig.…”

“…Coaxial electrospinning thus exhibits more steady release rate behaviour 8,[14][15][16] . In addition, the shell matrix of the fibre can be tailored to provide additional functional properties 17,18 . Nevertheless, encapsulation of orally administered bioactive compounds using coaxial electrospinning has rarely been attempted.…”