No abstract

Nanoreinforced polymers have gained popularity in the last decades since they exhibit enhanced properties (compared to pristine polymers) that are useful in a wide range of applications. Unfortunately, dispersion of nanoparticles (NPs) into polymeric matrices is a major problem since they tend to form agglomerates, limiting the improvement of properties and further applications. In this work, we propose the use of coaxial electrospinning as one-step method to disperse NPs in a polymeric matrix. Particularly, iron oxide (Fe 3 O 4) NP with a monomodal and bimodal size distributions were dispersed in polyvinylidene fluoride (PVDF), a material that is well known for its improved piezoelectric properties when it is processed via electrospinning. The results indicate that the incorporation of NP modified the polymeric fiber depending on their surface-to-volume ratio (smaller NP promoted smaller fiber size). Moreover, transmission electron microscopy revealed a good NP dispersion in the polymer, especially for the smallest NP size (monomodal). Finally, each NP size distributions were well preserved in the electrospun mats compared to the initial NP solutions, demonstrating the suitability of this technique for the fabrication of nanoreinforced PVDF structures with tailored NP size. Overall, this method could represent a facile and practical alternative to fabricate materials with piezoelectric/super-paramagnetic properties.

We report the feasibility of electrospinning of protein-polymer multilayered scaffolds with selected materials such as non-hydrolyzed silk sericin (SS), polyethylene oxide (PEO), and polylactic acid (PLA), with tuned fiber size and properties for each layer. We present a new innovative way for the electrospinning (ES) of non-hydrolyzed SS mixed with PEO yielding fibers with an average diameter ranging between 120 and 150 nm. Different SS:PEO ratios have been electrospun to study the effect of the concentration of SS protein on the fibers size and shape, as well and their electrospinnability. Electrospun SS:PEO fibers display weak to no mechanical resistance (non-measurable) and their deposition onto a sturdier scaffold is necessary to allow their use in biomedical and/or pharmaceutical fields. Therefore, bilayer scaffolds have been fabricated consisting of a PLA support and SS:PEO fibers obtained from the optimized SS:PEO ratio (1.2:4). They are composed of a sturdy hydrophobic layer of PLA fibers and a layer of sticky hydrophilic SS:PEO fibers. The scaffolds have been characterized extensively by Fourier transforms infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and their resistance to mechanical stress. Finally, hydrophobicity of both layers has been determined by measuring the contact angle of water droplets on the scaffolds, further proving the bilayer nature of the scaffolds.