Hybrid Silica–PVA Nanofibers via Sol–Gel Electrospinning

Abstract

We report on the synthesis of poly(vinyl alcohol) (PVA)-silica hybrid nanofibers via sol-gel electrospinning. Silica is synthesized through acid catalysis of a silica precursor (tetraethyl orthosilicate (TEOS) in ethanol-water), and fibers are obtained by electrospinning a mixture of the silica precursor solution and aqueous PVA. A systematic investigation on how the amount of TEOS, the silica-PVA ratio, the aging time of the silica precursor mixture, and the solution rheology influence the fiber morphology is undertaken and reveals a composition window in which defect-free hybrid nanofibers with diameters as small as 150 nm are obtained. When soaked overnight in water, the hybrid fibers remain intact, essentially maintaining their morphology, even though PVA is soluble in water. We believe that mixing of the silica precursor and PVA in solution initiates the participation of the silica precursor in cross-linking of PVA so that its -OH group becomes unavailable for hydrogen bonding with water. FTIR analysis of the hybrids confirms the disappearance of the -OH peak typically shown by PVA, while formation of a bond between PVA and silica is indicated by the Si-O-C peak in the spectra of all the hybrids. The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica could broaden the scope of use of these materials in various technologies.

Carbon-Confined PVA-Derived Silicon/Silica/Carbon Nanofiber Composites as Anode for Lithium-Ion Batteries

“…PVA nanofibers showed the and 836 cm −1 were attributed to the C-O-H stretching movement in aliphatic alcohols and out-of plane vibration of -CH. 30 For SiO 2 /PVA nanofibers, the peak at 1060 cm −1 was attributed to asymmetric Si-OSi stretching motion and the band at 930-950 cm −1 was attributed to Si-OH. The presence of Si-O-Si in the SiO 2 /PVA nanofibers demonstrates the formation of the silica network in the electrospun composite nanofibers.…”

“…From Figure 2, it is also seen that Si/SiO 2 /PVA nanofibers also had a characteristic SiO 2 peak at around 1100 cm −1 , corresponding to the symmetric stretching, asymmetrical stretching, and bending vibrations in Si-O-Si bonds. 30 The shoulder at around 1200 cm…”

“…When SiO 2 was formed in the PVA matrix, the -OH stretching peak of PVA at around 3300 cm −1 was reduced, which could be explained by the intermolecular interaction between the -OH groups of PVA and silica. [30][31][32] In addition, the broad Si-O-Si peak around 1100 cm −1 contained a shoulder at around 1200 cm −1 , which could be attributed to the reaction between -OH groups of PVA and silanol groups of silica. The formation of this new bond and the reduction of -OH bond intensity demonstrated that silica crosslinked with PVA and formed a network structure containing Si-O-PVA-O-Si bridges (Figure 3).…”

“…The molar ratio of the TEOS solution was TEOS:water:ethanol:HCl = 1:3:8:0.04. 30 The TEOS solution was stirred at room temperature for 3 h and was then gradually added to the PVA solution, followed by stirring for additional 3 h. Si …”

Microwave absorption properties of SiC@SiO2@Fe3O4 hybrids in the 2–18 GHz range

“…3. The strong bands at 800.99 and 926.50 cm −1 correspond to stretching vibrations of the Si-C bonds [26]. The peak at 1107.19 cm −1 corresponds to an Si-O antisymmetric stretching frequency and is attributed to the amorphous silica on the surface [27].…”