3 research outputs found
Enhancing the Effect of the Nanofiber Network Structure on Thermoresponsive Wettability Switching
This letter reports the enhancing effects of a nanofiber network structure on stimuli-responsive wettability switching. Thermoresponsive coatings composed of nanofibers were prepared by electrospinning from thermoresponsive polymer poly(<i>N</i>-isopropylacrylamide) (PNIPAAm). The nanofiber coatings showed a large amplitude of thermoresponsive change in the wettability from hydrophilic to hydrophobic states compared to a smooth cast film. In particular, the combination of the surface chemistry and unique topology of the electrospun nanofiber coatings enables a transition from the Wenzel state to the metastable Cassie–Baxter state with an increase in temperature and consequently an enhanced amplitude of change in the water contact angles: the apparent contact angle differences between 25 and 50 °C are Δθ*<sub>25–50 °C </sub>= 108 and 10° for the nanofiber coatings with a diameter of 830 nm and a smooth cast film, respectively. The fabrication of the 3D nanofiber network structure by electrospinning from stimuli-responsive materials is a promising option for highly responsive surfaces in wettability
Electrospun Composite Nanofiber Yarns Containing Oriented Graphene Nanoribbons
The graphene nanoribbon (GNR)/carbon
composite nanofiber yarns were prepared by electrospinning from polyÂ(acrylonitrile)
(PAN) containing graphene oxide nanoribbons (GONRs), and successive
twisting and carbonization. The electrospinning process can exert
directional shear force coupling with the external electric field
to the flow of the spinning solution. During electrospinning, the
well-dispersed GONRs were highly oriented along the fiber axis in
an electrified thin liquid jet. The addition of GONRs at a low weight
fraction significantly improved the mechanical properties of the composite
nanofiber yarns. In addition, the carbonization of the matrix polymer
enhanced not only the mechanical but also the electrical properties
of the composites. The electrical conductivity of the carbonized composite
yarns containing 0.5 wt % GONR showed the maximum value of 165 S cm<sup>–1</sup>. It is larger than the maximum value of the reported
electrospun carbon composite yarns. Interestingly, it is higher than
the conductivities of both the PAN-based pristine CNF yarns (77 S
cm<sup>–1</sup>) and the monolayer GNRs (54 S cm<sup>–1</sup>). These results and Raman spectroscopy supported the hypothesis
that the oriented GONRs contained in the PAN nanofibers effectively
functioned as not only the 1-D nanofiller but also the nanoplatelet
promoter of stabilization and template agent for the carbonization
Molecular Dynamics Study of Carbon Nanotubes/Polyamide Reverse Osmosis Membranes: Polymerization, Structure, and Hydration
Carbon
nanotubes/polyamide (PA) nanocomposite thin films have become very
attractive as reverse osmosis (RO) membranes. In this work, we used
molecular dynamics to simulate the influence of single walled carbon
nanotubes (SWCNTs) in the polyamide molecular structure as a model
case of a carbon nanotubes/polyamide nanocomposite RO membrane. It
was found that the addition of SWCNTs decreases the pore size of the
composite membrane and increases the Na and Cl ion rejection. Analysis
of the radial distribution function of water confined in the pores
of the membranes shows that SWCNT+PA nanocomposite membranes also
exhibit smaller clusters of water molecules within the membrane, thus
suggesting a dense membrane structure (SWCNT+PA composite membranes
were 3.9% denser than bare PA). The results provide new insights into
the fabrication of novel membranes reinforced with tubular structures
for enhanced desalination performance