Nanofiber mats preparation

The literature reports some examples of functional nanofiber mats prepared by simultaneously electrospinning a polymer solution and electrospraying a particle suspension on the same metallic collector. In electrospraying, when the electric force is higher than the surface tension of the liquid, the jets are atomized into fine droplets that are collected as solid particles. In electrospinning, the electric repulsion force cannot overcome the intermolecular forces in the liquid and, hence, the jet extends, bends and eventually reaches the collector, forming a solid fiber. The resulting nonwoven mat is composed of nanoparticles located on the fiber surface and within the pores of the nonwoven structure (Fig. 20). 

Polymer solution with concentration 15 wt. % was prepared by dissolving PAN in DMF. The PAN solution in DMF was loaded into a 1 ml syringe. A modified electro spinning system consists of two syringe pumps was used to produce bulky nanofiber mats. The experimental setup of electrospiiming has been shown in... 

The electric response of isolated PANI fibers to vapors of aliphatic alcohols depends on the laige surfece-to-volume ratio, the uniformity of diameter, and the quantity of active material. The sensor constructions are comparable to or faster than those prepared from nanofiber mats of the same polymer. Also, the sensors made from individual fibers exhibit larger responses, especialty for bigger alcohol molecules, and also show true saturation upon exposure and removal of the alcohol vapor. The response of sensors made from electrospun nanofibers to small alcohol molecules is opposite to that observed for cast nanofiber mats, which can be related to the doping process used in the preparation of the polymer in either case. ... 

Conductivity measurements were realized using broadband dielectric spectrometer. Nanofiber mat samples were prepared with the area of 4 cm for measurement As a result, conductivity values increased with an increase of PEDOT-PSS content at high frequency. Figure 5.19 shows the conductivity changes with the increase of the CP in the nanofiber composite. 

Two types of poly electrolyte nanofiber mats were prepared in this study. One was polyacrylic acid (Mv = 450,000) fibers, spun from 5 wt% of aqueous solution. The other one was polysulfone fibers, spun from 25 wt% of DMF solution. The polysulfone fiber was then coated with a layer of polyelectrolyte, FAMPS, by a surface grafting technique (FAMFS-g-FS) similar to the procedure described previously. Nucrel membranes wereprepared by heat pressing Nucrel 535 (DuPont) pellets at 125°C. For fiber encapsulation, the fiber mats with measured weight and thickness were placed between two preweighed Nucrel membranes and then pressed at 125°C. The resulting composite membranes were flexible and robust with a homogeneous transparency. 

The authors successfully prepared chemically cross-linked temperature-responsive electrospun nanofibers by thermal curing [llj. As a member of the NIPAAm family, N-hydroxymethylacrylamide (HMAAm) was copolymerized with NIPAAm by free-radical copolymerization because temperature-responsive HMAAm can be cross-linked by self-condensation at high temperatures (above 110°C). As a result of cross-linking, very stable nanofibers in aqueous solution were obtained and manipulated as a bulk material. By extension of the above-mentioned examples, the authors successfully prepared temperature-responsive electrospun nanofibers by photocuring [12]. The temperature-responsive nanofiber mats were prepared using the copolymers NIPAAm and 2-carboxyisopropylacrylamide conjugated to 4-aminobenzophenone, a photoinitiator. The crosslinked temperature-responsive nanofibers were obtained by UV irradiation for 30 min (Fig. 5.4.3). Chemically cross-linked nanofibers were also reported by... 

Vitchuli et al. [174] used the combined technologies to prepare a multifunctional ZnO/nylon-6 nanofiber mat with antibacterial and detoxifying properties for use in protective applications. Nylon-6 polymer solution and a ZnO NP dispersion were loaded into two separate syringes and placed side-by-side on a two-syringe pump. In the resulting material, ZnO particles were attached to the nanofiber surface and were distributed throughout the entire mat. 

This optimum condition was a predicted value, thus to confirm the predictive ability of the RSM model for response, a further electrospinning was carried out according to the optimized conditions and the agreement between predicted and measured responses was verified. The measiued CA of electrospim nanofiber mat (21°) was very close to the predicted value estimated to 20°. Figure 11 shows the SEM image and AFD distribution of electrospim fiber mat prepared at optimized conditions. 

Jeong, E. H., J. Yang, J. H. Youk, Preparation of polyurethane cationomer nanofiber mats for use in antimicrobial nanofilter applications. Materials Letters, 2007, 61(18), 3991-3994. 

Figure 5.10 Tensile test piece preparation with fragile nanofiber mats. Redrawn from Huang et al. (2004),...

---