Dispersion composite nanofibers

It is reasonable that, in the synthesis of polymer nanocomposites, the y-ray irradiation method is convenient for growing nanofibers and nanowires of metal chalcogenides due to the shape-control of the macromolecules formed in situ. Figure 7.38 shows some of the resulting nanofiber-dispersed polymer composites,... 

A gas-solid reaction was further introduced to the electrospiiming technique to incorporate semiconductor nanostructures into polymer nanofibers with better dispersion. The production of well-dispersed PbS nanoparticles in polymer fiber matrices has been achieved by this method (Lu et al., 2005). First, metal salt and polymer were codissolved into one solvent to make a homogeneous solution. Then the above solution was electrospun to obtain polymer/metal salt composite nanofibers. The composite nanofibers were finally exposed to HaS gas at room temperature to synthesize PbS nanoparticles in situ in polymer nanofibers. 

King et at fabricated PANI/CNT composite nanofibers with different types of CNTs through CNT-templated in-situ polymerization by using APS as oxide and methane sulfonic as dopant [9]. Liu et at prepared flexible PANI/SWNT composite films by in-situ electrochemical polymerization process [10]. The morphology and microstructure of the composite can be finely adjusted through the modulation of electrolyte component and electric current. In addition to PANI/CNT composites, poly(3-hexyl-thiophene) (P3HT)/MWNT composites have also been prepared by in-situ polymerization of 3-hexylthiophene in MWNTs-dispersed chloroform solution [11]. 

It has been established that electrospinning a polymer solution containing well-dispersed carbon nanotubes leads to nanocomposite fibers with the embedded carbon nanotubes oriented parallel to the nanofiber axis due to the large shear forces in a fast fiber-drawing process. Table 1 lists most of the polymer/CNT composite nanofibers produced by electrospining, along with their fiber diameters and tensile properties. 

Ko et al. (2003) electrospun composite nanofibers of PAN with dispersed SWCNTs from DMF solutions and reported their orientation in the axial direction in the fiber. Using an AFM-based indentation technique (see Chapter 5), the modulus of the composite PAN fibers (as opposed to that of fiber mats) was measured. The modulus of the nanofibers increased linearly with the volume fraction of CNTs incorporated. Interestingly, the increases were also higher (by a factor of more than two) than that expected on the basis of the mle of mixtures calculated assuming a value of 1 TPa for... 

Diffraction of the (002) crystal plane from MWCNT (at 2d 27°) is quite distinct from the difhaction due to the (200) crystal plane from the PAN, which is seen at 26 15-20°. Figure 6.6 shows the WAXD results, comparing the spectra for PAN with those for PAN/MWCNT composite nanofibers with different volume fractions of CNTs dispersed (as indicated in the caption of the Fig. 6.6). Peaks due to CNT content generally tend to be sharper than those due to polymer (Hou et al. 2005). The peak corresponding to the (002) crystal plane of the MWCNT increases with CNT content and allows quantification of the nanotubes in composite. 

Figure 6.7 X-ray diffraction patterns for PEO nanofibers with the dispersant sodium dodecyi suifate (a) control nanofibers (b) composite nanofibers with MWCNTs. Reprinted with permission from Dror et al. (2003). Copyright 2003. American Chemicai Society.

MMT is a reinforcing filler in polymers such as poly(urea urethane) (Ge et al. 2000) as evidenced by the very significant increase in mechanical properties of the composite nanofibers. Unfilled polymer nanofiber mats of polyurethane (PU) (M — 150,000 g/mol) were electrospun from llwt% solution in DMAc/THF (7 3wt/wt) into nanofibers with 150nm to 410nm. The tensile properties of these mats are shown in Table 6.4, where the last digit in the nanofiber designation is the weight fraction of MMT in the polymer. Based on the WAXD patterns for the composite nanofibers, MMT appeared to be well dispersed, exfoliated, and oriented in the axial direction of the samples. 

A free-standing CNT/Li4Ti50i2/C composite nanofiber with Li4Ti50i2 nanoparticles and CNTs uniformly dispersing in a ID carbon nanofiber matrix was also reported to deliver a good rate capability as anode material for Na-ion batteries [148]. Yu et al. [147] revealed the peseudocapacitive behavior of Li4Ti50i2 upon Na ion insertion, especially for nanoparticles with sufficient surface defects, which contribute much of the specific capacity and rate-capability without trade-off of structural phase transformation. 

Ti02/fluoropolymer composite nanofibers by combining the electrospinning technique and hydrothermal complex-precipitation [115], The obtained Ti02 nanoparticles were well dispersed on the surface of fluoropolymer nanofibers. The photocatalytic activity of the as-prepared TiOo/fiuoropolymer composite nanofibers is higher than that of P25 nanoparticles (Fig. 15.10). Moreover, the good recycling and stability of the composite nanofibers enable them to be applicable in the wastewater treatment. 

Liu F, Ni QQ, Murakami Y (2013) Preparation of magnetic polyvinyl alcohol composite nanofibers with homogenously dispersed nanoparticles and high water resistance. Text Res J 83(5) 510-518. doi 10.1177/0040517512444334... 

The polymer resulting from oxidation of 3,5-dimethyl aniline with palladium was also studied by transmission electron microscopy (Mallick et al. 2005). As it turned out, the polymer was formed in nanofibers. During oxidative polymerization, palladium ions were reduced and formed palladium metal. The generated metal was uniformly dispersed between the polymer nanofibers as nanoparticles of 2 mm size. So, Mallick et al. (2005) achieved a polymer- metal intimate composite material. This work should be juxtaposed to an observation by Newman and Blanchard (2006) that reaction between 4-aminophenol and hydrogen tetrachloroaurate leads to polyaniline (bearing hydroxyl groups) and metallic gold as nanoparticles. Such metal nanoparticles can well be of importance in the field of sensors, catalysis, and electronics with improved performance. 

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