PANI-AMPSA

The PANi-AMPSA spinning solution containing CNTs was prepared based on the method reported previously [18]. The fibers were then spun according to previously reported procedures [18],... 

FIGURE 2 The influence of CNT content on the viscosity of solutions containing PANi-AMPSA (11.5% (w/w)). The weight fraction of SWNT is given with respect to the weight of... 

TABLE 1 Influence of SWNTs loading on mechanical properties of PANi-AMPSA fibers... 

FIGURE 4 Typical stress - strain curves for (0) neat PANi-AMPSA and (o) PANi-AMPSA-SWNT (0.76% (w/w) SWNTs). 

The effect of S WNT addition to PANi fibers on conductivity was also investigated (Figure 8). A percolation threshold of 0.35% (w/w) SWNTs was determined using the basic percolation power law [32]. The value for conductivity percolation threshold obtained here is in good agreement with another polymer-nanocomposite system that showed a 0.5 w/w % percolation level [33]. In addition, a significant increase in electrical conductivity was observed even at low SWNTs loadings, while the neat PANi-AMPSA fibers prepared here had similar conductivities ( 500 Scm ) compared to those obtained in a previous study (600 Scm ) [11]. 

FIGURE 5 Cross-sectional SEM of neat PANi-AMPSA fiber. Scale bar (a) 20 pm (b) 1 pm. 

FIGURE 7 SEMs of knotted (a) PANi-AMPSA and (b) PANi-AMPSA-SWNT (0.76 % (w/w) SWNTs). 16 ply twisted fiber (TPI=36) of PANi - AMPSA- SWNT (0.76% w/w) with (c) S shaped twisting(d) Z shaped twisting. 

FIGURE 8 Electrical conductivity of PANi-AMPSA-SWNT composite fibers as a function of CNT loading. 

TABLE 2 Assigned Raman absorption frequencies originating from PANi-AMPSA-SWNT composite fibers. exc = 632.8 nm. 

FIGURE 9 Enhanced Raman spectra = 632.8 nm) obtained for PANi-AMPSA-SWNT composite fibers containing various SWNT loadings (a) 0% (w/w), (b) 0.26% (w/w), (c) 0.38% (w/w) and (d) 0.52% (w/w). Enhanced Raman spectrum of SWNTs bucky paper (f). 

FIGURE 10 Cyclic voltammograms of (a) neat PANi-AMPSA and (b) SWNT-reinforced PANi-AMPSA fibers. Potential was scanned between - 0.2 V and + 0.5 V (vs. Ag/AgCl) in 1 M HCl,, at 5 mVs. ... 

The addition of CNTs to PANi-AMPSA fibers processed from DC A A resulted in materials with high conductivity, high mechanical strength and modulus. Conductivities as high as 750 Scm were achieved in continuously spun fibers up to 50-100 m in length. 

FABRICATION OF PANI/AMPSA-SWNT FIBRE SMLES... 

The o(T) of 2-acrylamido-2-methyl-l-propane-sulfonic acid (AMPSA) samples are shown in Figure 2.6 [38, 39]. These samples show a positive TCR at temperatures above 80 K. Although the o(300 K) of PANI-AMPSA samples is slightly lower with respect to PANI-CSA, its positive TCR is observed down to much lower temperatures. The wet spun PANI-AMPSA fibres have shown an impressive room temperature conductivity of nearly 2000 S cm [40]. The difference in o(300 K) and o(T) between CSA- and AMPSA-doped PANI samples is possibly due to the variations in microstructure and its contribution to disorder-induced localisation. This shows that the charge transport in doped conducting polymers is rather sensitive to slight variations in the morphological features. 

Figure 2.6 Conductivity versus temperature for PANI-AMPSA samples at various doping levels mentioned in subscripts...

The metallic positive TCR has been observed from 300 to 1.5 K in C104-doped (CH), . In PANI-AMPSA (CSA) the positive TCR is observed at temperatures greater than 70 (150) K. In several metallic conducting polymer samples a positive TCR has been observed at temperature below 20 K. These features show the intrinsic metallic... 

In the preparation of these concentrated PANI-AMPSA/DCAA solutions according to the procedures reported by Monkman and coworkers [59-61], it was noticed that the high-molecular-weight EB powders, which had been dried in the vacuum oven (water content <0.5 wt%), had difficulty wetting upon addition to the DCAA solvent. This problem could be overcome by the addition of a trace amount of water to the EB powder before it was dissolved in the DCAA solvent. However, there was a finite water limit. Above 30 wt% water in EB powder, the nascent fiber flattened and fell apart in the coagulation bath. Furthermore, it was found that fiber with good mechanical properties could only be spun if the water content in the EB powders was between 2 and 10 wt%. Thus, with appropriate mixing conditions, PANI-AMPSA/DCAA dope solutions with a total solids content between 4.5 and 14 wt% may be prepared... 

The fibers that are described in the following section were spun from a 12 wt% PANI-AMPSA/DCAA dope solution with the high-molecular-weight polyaniline synthesized in-house (M 280,000 g/mol). 

The water content relative to the EB powder was between 2 and 10 wt% since these solutions yield fibers with good mechanical and electrical properties. This corresponds to an overall percentage of water in these PANI-AMPSA/DCAA solutions between 0.1 and 0.6 wt%. The ratio of the number of AMPSA molecules to the number of nitrogen atoms in the polyaniline was 0.6. A description of the spin line is identical to the one described earlier for fabricating the polyaniline fibers using the base-processing route (Section 2.3.3). 

FIGURE 2.23 Rheological behavior of a 7 wt% total solids PANI-AMPSA/DCAA solution. 

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