PEO nanofiber mats

Figure 4.12 PEO nanofiber mats electrospun under identical conditions except (a) +7500 V AC was applied and (b) 7000 V DC was applied, showing differences in fiber alignment. Reproduced with permission from Kessick et al. (2004). Copyright 2004. Elsevier.

Fig. 16.7 SEM (al, bl, cl) and TEM (a2, b2, c2) images of the silver nanoparticles/PEO nanofiber mats fabricated from aqueous solution of 4 wt% 600 kDa PEO and AgNOs at concentrations of (a) 0, (b) 0.17, and (c) 0.26 wt% (Reproduced from Ref. [43] by permission of John Wiley Sons Ltd)...

Vondran et al. [170] reported electrospun chitosan/PEO nanofiber mats cross-linked with GA and eompared them with ones without cross-linking. Results showed mechanical properties ehange with exposure time but generally cross-linking tended to increase the stiffiiess and deerease the duetility of the electrospun mats. 

In order to improve the properties and the spinnability, fibroin sometimes has been electrospun together with other natural or synthetic polymers (Jin et al., 2002 Park et al., 2004, 2006 Wang et al., 2004, 2006). For instance, Jin et al. (2002) developed an aqueous process for silk electrospinning in combination with PEO. More recently, Cao (2008) used PVA/Silk Fibroin (SF), Gelatin/SF, and Hydroxyapatite (HAP)/SF to produce double-layered (core-shell) nanofibers (mats) by coelectrospinning. 

The sheet conductivities of the PPy-PEO composite nanofiber mats were in the order of 10" S/cm calculated from the four-probe measurement data. Conductivities of electrospun nanofibers measured by using the four-probe method were about 10" S/cm. PPy was coated on PS nanofiber mats, and the conductivities of the PS-Cl-PPy and PS-TS-PPy fiber mats were found to be 2 x 10" S/ cm and 5 x 10 S/cm, respectively. It was demonstrated that the conductivity of the porous fiber mat could be influenced by the amount (PPy/PS ratio), doping, and crystallinity (polymer chain packing) of PPy in the fibers, the void volume, and the connectivity between fibers in the mat. When the PS template of the PS-TS-PPy fiber mat was removed by THF treatment and the electrical conductivity of the remaining material (TS-PPy) was measured, the conductivity increased to 0.13 S/cm by using the four-probe Van der Pauw method. ... 

Ultrafine fibers of PANl doped with CSA were blended with PEO by electrospinning. By controlling the ratio of PANl to PEO, desired conductivities were obtained. The comparison between cast films and nanofiber mats was reported. High porosity of nanofiber mats leads to lower conductivities compared to cast films but nanofiber mats have advantages like quick dedoping due to a higher surface area. 

Chondrocytes (Bhattarai et al. 2005 Suhramanian et al. 2005) and osteoblasts (Bhattarai et al. 2005) were shown to grow well on chitosan blend nanofibers. In a comparative study, cell viability on polymer film, nanofiber mat and PS surfaces has been reported. Chondrocyte cell proliferation (10 days of culture) on the chitosan/PEO scaffolds was 81% of that obtained for tissue-culture-grade polystyrene surfaces while that for film geometry was about 56% (Suhramanian et al. 2005). 

Electrospinning processes are used to prepare nanocomposite fiber mats. In order to prepare nanocomposite fiber mats, mixtures containing the polymer solution and cellulose whiskers solution are placed in the appropriated electrospinning setup. Peresin et al. [128] have produced nanocomposite mats of poly (vinyl alcohol) (PVA) reinforced with cellulose nanocrystals using this electrospinning technique. Smooth nonwoven mats with homogeneous nanofibers were obtained. Park et al. [129] have also incorporated cellulose whiskers into nanofibers of polyethylene oxide (PEO) by the electrospiiming process. 

To improve PANI processability, the first approach to obtain polyaniline doped with camphorsulfonic acid (PANI-CSA) and doped nanofibers blended with common pol5miers by electrospinning was done by MacDiarmid s group. In another study a nonwoven mat was obtained by using a PANI/poly(ethylene oxide) (PEO) solution dissolved in chloroform. By controlling the ratio of PANI to PEO in the blend, fibers with conductivity values comparable to that of PANI-CSA/PEO cast films were produced. 

Another modified spinneret was designed with multiple single jets in order to enhance nanofibers spinning rate of PEO (Theron et al. 2005) or to prepare nanofibrous mats composed of two different and immiscible polymers such as PVA and cellulose acetate. A multiple jet composed of four tips was used in order to blend PVA and cellulose acetate nanofibers in different ratios (Pham et al. 2006). In another study, a collector moving transversely was used in front of a multiple jet composed of two tips in order to produce a mixture of electrospun PEO and polyurethane (PU) nanofibers and a uniform distribution of this mixture was achieved due to the motion of the collector (Kidoaki et al. 2005). 

Progress made in electrospinning in the past decade has allowed for the production of fibers in nanoscale diameters from various polymers. Tissue engineering has benefited a lot from this process and quite often silk protein is used to produce nanofiber scaffolds for ceU cultures. Human bone marrow stromal cells were found to proHferate in vitro very well on mats made from poly(ethylene oxide) (PEO) and B. mori silk aqueous solution electrospun nanofibers [27]. A very interesting work by... 

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