Electrospun Ultrafine Fiber Composites Containing Fumed Silica: From Solution Rheology to Materials with Tunable Wetting

Abstract

Fumed silica (FS) particles with hydrophobic (R805) or hydrophilic (A150) surface functionalities are incorporated in polyacrylonitrile (PAN) fibers by electrospinning to produce mats with controlled wettability. Rheological measurements are conducted to elucidate the particle-polymer interactions and characterize the system while microscopic and analytic tools are used to examine FS location within both fibers and films to aid in the fundamental understanding of wetting behavior. Unlike traditional polymers, we find these systems to be gel-like, yet electrospinnable; the fumed silica networks break down into smaller aggregates during the electrospinning process and disperse both within and on the surface of the fibers. Composite nanofiber mats containing R805 FS exhibit an apparent contact angle over 130° and remain hydrophobic over 30 min, while similar mats with A150 display rapid surface-wetting with a static contact angle of ∼30°. Wicking experiments reveal that the water absorption properties can be further manipulated, with R805 FS-impregnated mats taking up only 8% water relative to mat weight in 15 min. In contrast, PAN fibers containing A150 FS absorb 425% of water in the same period, even more than the pure PAN fiber (371%). The vastly different responses to water demonstrate the versatility of FS in surface modification, especially for submicron fibrous mats. The role of fumed silica in controlling wettability is discussed in terms of their surface functionality, placement on nanofibers and induced surface roughness.

Interfacing Graphene-Based Materials With Neural Cells

“…Each carbon atom has three μ-bonds and an out-of-plane π-bond that can bind with neighboring atoms (Geim, 2009 ), making G the thinnest compound ever known at one atom thick and the strongest compound discovered. Moreover, it is light, flexible and transparent and both electrically and thermally highly conductive, which opens the possibility of using it in a broad spectrum of applications, including supercapacitors (Hess et al, 2011 ; Sahoo et al, 2015 ; Casaluci et al, 2016 ), flexible electronics (Eda et al, 2008 ; Meric et al, 2008 ), printable inks (Zhu et al, 2015 ; Bonaccorso et al, 2016 ), batteries (Hassoun et al, 2014 ; Dufficy et al, 2015 ), optical and electrochemical sensors (Pumera, 2009 ; Du et al, 2010 ; Kang et al, 2010 ), energy storage (El-Kady and Kaner, 2013 ; Bonaccorso et al, 2015 ; Ambrosi and Pumera, 2016 ) and medicine (Novoselov et al, 2012 ; Casaluci et al, 2016 ; Kostarelos et al, 2017 ; Reina et al, 2017 ). G-related materials (GRMs) include single- and few-layered G (1–10 layers; GR), G oxide (single layer, 1:1 C/O ratio; GO), reduced G oxide (rGO), graphite nano- and micro-platelets (more than 10 layers, but <100 nm thickness and average lateral size in the order of the nm and μm, respectively), G and G oxide quantum dots (GQDs and GOQDs, respectively), and a variety of hybridized G nanocomposites (Bianco, 2013 ; Wick et al, 2014 ; Cheng et al, 2016 ).…”

Preparation and Properties of Electrospun Poly (Vinyl Pyrrolidone)/Cellulose Nanocrystal/Silver Nanoparticle Composite Fibers

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Reversible Structure Formation of Aluminum Trihydroxide (ATH) Dispersions in Polydimethylsiloxane (PDMS)

“…Critical Water Concentration. In order to determine the critical water concentration that marks the onset of weak to strong gel transition, 36 we conducted a series of strain amplitude sweeps at a constant frequency (1 Hz) for ATH/ PDMS dispersions at various ATH loadings as a function of water content. Figure 2 shows G′ from the LVE regime plotted as a function of water concentration for various ATH loadings while Figure S2 shows strains sweeps for a representative 20 vol % ATH/PDMS sample at various water concentrations.…”