Molecular weight driven structure formation of PEG based e-spun polymer blend fibres

Abstract

Electrostatic spinning of polymer blends offers the potential to obtain functionalised nano- to micron-scaled fibres which combine the properties of the blend components. In tissue engineering for instance, the surface chemistry incorporates, besides mechanical and morphological properties, a key role for enhanced cell proliferation and differentiation. Therefore we developed porous fibre non-wovens with tuneable wettability properties by use of a one step electrospinning procedure and the use of polymer blends with defined molecular weight (MW) ratios.Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDFhfp) and poly(ethylene glycol) (PEG) were mixed with constant weight ratios but varying PEG MW's. Electrostatic spinning of these solutions reveals fibre morphologies with increasing diameters in function of the MW. By addition of small amounts of nanosized TiO2 particles stable fibre diameter were found due to an increase of the electrical conductivity of the spinning dispersions. Interestingly, polymer MW has a great impact on fibre structure and surface chemical composition, respectively. High surface concentrations of oxygen and thus PEG within the sheath are found for high MW's, whereas most of the low MW PEG is located within the fibre core. It is suggested, that polymer molecular chain mobility as well as polymer solubilities are the key factors influencing the mechanism of fibre formation and thus the final distribution and morphology of the polymers within the fibres. These results are underpinned by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), static water contact angles and rheological measurements.